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<span><div><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">转自：http://blog.csdn.net/zhangerqing/article/details/8466532</p><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       本篇主要讲述IO相关的内容，主要包括：与IO相关的简单的历史背景知识；Java IO的简单分类；与IO设计相关的两个模式；同时列举几个简单的例子；分析其中几个实现的源代码；最后给大家一些简单扩展的例子。治学先治史，下面我们先从简单的历史开始吧！</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"> </div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><strong>一、      历史背景</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       “对语言设计人员来说，创建好的输入／输出系统是一项特别困难的任务。”</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">――《Think in Java》</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       无论是系统、还是语言的设计中IO的设计都是异常复杂的。面临的最大的挑战一般是如何覆盖所有可能的因素，我们不仅仅要考虑文件、控制台、网络、内存等不同的种类，而且要处理大量的不同的读取方式，如：顺序读取、随机读取，二进制读取、字符读取，按行读取、按字符读取……</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       Linux是第一个将设备抽象为文件的操作系统，在Linux中所有的外部设备都可以用读取文件的方法读取，这样编程人员就可以以操作文件的方法操作任何设备。C++在IO方面也做了一些改进――引进了流的概念，我们可以通过cin、cout读写一些对象。Java语言在IO设计方面取得较大的成功，它是完全面向对象的，主要采用装饰器模式避免大量的类，包括了最大的可能性，提供了较好的扩展机制……</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       “Java库的设计者通过创建大量类来攻克这个难题。事实上，Java的IO系统采用了如此多的类，以致刚开始会产生不知从何处入手的感觉（具有讽刺意味的是，Java的IO设计初衷实际要求避免过多的类）。” 上面一段来自《Think in Java》，确实很多初学者刚刚学习java的IO时会比较茫然，不过等我们知道装饰器模式（Decorator）的用意、场景及其在Java的IO包中的使用，你可能会真正领会整个IO的FrameWork。</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><strong>二、IO的分类</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">    Java IO一般包含两个部分：1.java.io包中堵塞型IO；2.java.nio包中的非堵塞型IO，通常称为New IO。学过操作系统的朋友都知道系统运行的瓶颈一般在于IO操作，一般打开某个IO通道需要大量的时间，同时端口中不一定就有足够的数据，这样read方法就一直等待读取此端口的内容，从而浪费大量的系统资源。有人也许会提出使用java的多线程技术啊！但是在当前进程中创建线程也是要花费一定的时间和系统资源的，因此不一定可取。Java New IO的非堵塞技术主要采用了Observer模式，就是有一个具体的观察者和＝监测IO端口，如果有数据进入就会立即通知相应的应用程序。这样我们就避免建立多个线程，同时也避免了read等待的时间。不过本篇主要讲述java的堵塞型IO，就是我们通常应用的那个包。</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">    打开你的java.io包你可以看到Java的IO包含大量的类和接口（JDK1.6中包含83个类或者接口），如此众多的类和接口似乎无从下手。下面就将IO简单地分类。Java的IO主要包含三个部分：1.流式部分――IO的主体部分；2.非流式部分――主要包含一些辅助流式部分的类，如：File类、RandomAccessFile类和FileDescriptor等类；3.文件读取部分的与安全相关的类，如：SerializablePermission类。以及与本地操作系统相关的文件系统的类，如：FileSystem类和Win32FileSystem类和WinNTFileSystem类。</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; font-family: Arial; font-size: 14px; color: rgb(217, 106, 37); background-color: rgb(255, 255, 255);">      <span style="font-family: mceinline;"> 流式部分可以概括为：两个对应一个桥梁。两个对应指：1.字节流（Byte Stream）和字符流（Char Stream）的对应；2.输入和输出的对应。一个桥梁指：从字节流到字符流的桥梁。对应于输入和输出为InputStreamReader和OutputStreamWriter。</span></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       在流的具体类中又可以具体分为：1.介质流（Media Stream或者称为原始流Raw Stream）――主要指一些基本的流，他们主要是从具体的介质上，如：文件、内存缓冲区（Byte数组、Char数组、StringBuffer对象）等，读取数据；2.过滤流（Filter Stream）――主要指所有FilterInputStream/FilterOutputStream和FilterReader/FilterWriter的子类，主要是对其包装的类进行某些特定的处理，如：缓存等。</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"> </div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><strong>三、IO中的流</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       流具有最基本的特点：“One dimension , one direction .” 即流是一维的，同时流是单向的。关于维和我们通常说的一维长度，二维平面，三维空间，四维时空……是同一个概念，流就是一维的。单向就是只可以一个方向（按顺序从头至尾依次）读取，不可以读到某个位置，再返回前面某个位置。流的概念和实际水流的概念基本一致，水只可以从高向低一个方向流动。我们某时在目地喝了一口水，下次在同一个地点喝水已经不是当时的那片水了。</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       流的这种特性在JMS（Java Message Service）的API设计中得到了体现。JMS是J2EE平台下面向消息中间件的一个标准。（关于中间件技术有机会和大家探讨）JMS中有五种具体类型的消息，这些消息一般分为两类：1.流式的消息――包含ByteMessage和StreamMessage；2.非流式的消息――包含TextMessage、ObjectMessage和MapMessage。我们在明白IO中流的特点后，基本可以明白JMS API设计者的意图。</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       可能有些场合我们需要在文件中随机插入数据、在流中来来回回地执行某些操作，这时候我们绝对不可以使用流相关的对象。很幸运JDK的设计者为我们设计了一个单独的类RandomAccessFile，它可以完成打开、关闭文件、以基本数据类型的方式读取数据、读取下一个行、以UTF等格式读取数据、写入各种类型的数据、比较特殊的是他可以通过文件指针的seek方法让文件指针移到某个位置，可以通过<a>getFilePointer方法得到当前指针的位置、可以通过length（）方法得到当前文件的容量、通过</a><a>getFD得到</a><a>FileDescriptor对象，通过</a><a>getChannel方法得到</a><a>FileChannel对象，从而和New IO整合。</a>()()()</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       下面比较简单的分析IO中的各个对象吧！</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><strong>3.1 IO中的输入字节流</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       下面是IO中输入字节流的继承图。</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">o        <strong>InputStream</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">o        <strong>ByteArrayInputStream</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">o        <strong>FileInputStream</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">o        <strong>FilterInputStream</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">o        <strong>BufferedInputStream</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">o        <strong>DataInputStream</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">o        <strong>LineNumberInputStream</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">o        <strong>PushbackInputStream</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">o        <strong>ObjectInputStream</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">o        <strong>PipedInputStream</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">o        <strong>SequenceInputStream</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">o        <strong>StringBufferInputStream</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">在上面的关系图中可以看出：<br/>
1.InputStream是所有的输入字节流的父类，它是一个抽象类。<br/>
2. ByteArrayInputStream、StringBufferInputStream、FileInputStream是三种基本的介质流，它们分别将Byte数组、StringBuffer、和本地文件中读取数据。PipedInputStream是从与其它线程共用的管道中读取数据，与Piped相关的知识会用专门的一小节讲解。<br/>
3. ObjectInputStream和所有FilterInputStream的子类都是装饰流（装饰器模式的主角）。下表列出了这些流的功能及如何使用它们（具体使用在讲解完装饰器模式后会举几个例子）。</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">基本输入字节流：</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><table border="1" cellpadding="0" style="border-collapse: collapse;"><tbody><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="155"><strong>类</strong></td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="192"><strong>功能</strong></td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="203"><strong>如何构造</strong></td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="203"><strong>怎样使用</strong></td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="155">ByteArrayInputStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="192">将内存中的Byte数组适配为一个InputStream。</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="203">从内存中的Byte数组创建该对象（2种方法）</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="203">一般作为数据源，会使用其它装饰流提供额外的功能，一般都建议加个缓冲功能。</td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="155">StringBufferInputStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="192">将内存中的字符串适配为一个InputStream。</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="203">从一个String对象创建该对象。底层的实现使用StringBuffer。该类被Deprecated。主要原因是StringBuffer不应该属于字节流，所以推荐使用StringReader。</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="203">一般作为数据源，同样会使用其它装饰器提供额外的功能。</td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="155">FileInputStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="192">最基本的文件输入流。主要用于从文件中读取信息。</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="203">通过一个代表文件路径的 String、File对象或者 FileDescriptor对象创建。</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="203">一般作为数据源，同样会使用其它装饰器提供额外的功能。</td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="155">PipedInputStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="192">读取从对应PipedOutputStream写入的数据。在流中实现了管道的概念。</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="203">利用对应的PipedOutputStream创建。</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="203">在多线程程序中作为数据源，同样会使用其它装饰器提供额外的功能。</td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="155">SequenceInputStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="192">将2个或者多个InputStream 对象转变为一个InputStream.</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="203">使用两个InputStream 或者内部对象为InputStream 的Enumeration对象创建该对象。</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="203">一般作为数据源，同样会使用其它装饰器提供额外的功能。</td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="155">FilterInputStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="192">给其它被装饰对象提供额外功能的抽象类</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="203">主要子类见下表</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="203"> </td></tr></tbody></table></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">装饰、输入字节流：</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><table border="1" cellpadding="0" style="border-collapse: collapse;"><tbody><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="159"><strong>类</strong></td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="178"><strong>功能</strong></td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="197"><strong>如何构造</strong></td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="197"><strong>怎样使用</strong></td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="159">DataInputStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="178">一般和DataOutputStream配对使用,完成基本数据类型的读写。</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="197">利用一个InputStream构造。</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="197">提供了大量的读取基本数据类新的读取方法。</td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="159">BufferedInputStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="178">使用该对象阻止每次读取一个字节都会频繁操作IO。将字节读取一个缓存区，从缓存区读取。</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="197">利用一个InputStream、或者带上一个自定义的缓存区的大小构造。</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="197">使用InputStream的方法读取，只是背后多一个缓存的功能。设计模式中透明装饰器的应用。</td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="159">LineNumberInputStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="178">跟踪输入流中的行号。可以调用getLineNumber( )和 setLineNumber(int)方法得到和设置行号。</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="197">利用一个InputStream构造。</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="197">紧紧增加一个行号。可以象使用其它InputStream一样使用。</td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="159">PushbackInputStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="178">可以在读取最后一个byte 后将其放回到缓存中。</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="197">利用一个InputStream构造。</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="197">一般仅仅会在设计compiler的scanner 时会用到这个类。在我们的java语言的编译器中使用它。很多程序员可能一辈子都不需要。</td></tr></tbody></table></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><strong>3.2 IO中的输出字节流</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       下面是IO中输出字节流的继承图。</div><ul style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><li> </li><li style="list-style: none; display: inline"><ul><li>OutputStream</li></ul></li></ul><ul style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><li> </li><li style="list-style: none; display: inline"><ul><li> </li><li style="list-style: none; display: inline"><ul><li>ByteArrayOutputStream</li><li>FileOutputStream</li><li>FilterOutputStream</li></ul></li></ul></li></ul><ul style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><li> </li><li style="list-style: none; display: inline"><ul><li> </li><li style="list-style: none; display: inline"><ul><li> </li><li style="list-style: none; display: inline"><ul><li>BufferedOutputStream</li><li>DataOutputStream</li><li>PrintStream</li></ul></li><li>ObjectOutputStream</li><li>PipedOutputStream</li></ul></li></ul></li></ul><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">在上面的关系图中可以看出：1.OutputStream是所有的输出字节流的父类，它是一个抽象类。2. ByteArrayOutputStream、FileOutputStream是两种基本的介质流，它们分别向Byte数组、和本地文件中写入数据。PipedOutputStream是向与其它线程共用的管道中写入数据， 3. ObjectOutputStream和所有FilterOutputStream的子类都是装饰流。下表列出了输出字节流的功能及如何使用它们。</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><table border="1" cellpadding="0" style="border-collapse: collapse;"><tbody><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="141"><strong>类</strong></td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="188"><strong>功能</strong></td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="213"><strong>如何构造</strong></td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="213"><strong>怎样使用</strong></td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="141">ByteArrayOutputStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="188">在内存中创建一个buffer。所有写入此流中的数据都被放入到此buffer中。</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="213">无参或者使用一个可选的初始化buffer的大小的参数构造。</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="213">一般将其和FilterOutputStream套接得到额外的功能。建议首先和BufferedOutputStream套接实现缓冲功能。通过toByteArray方法可以得到流中的数据。（不通明装饰器的用法）</td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="141">FileOutputStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="188">将信息写入文件中。</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="213">使用代表文件路径的String、File对象或者 FileDescriptor对象创建。还可以加一个代表写入的方式是否为append的标记。</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="213">一般将其和FilterOutputStream套接得到额外的功能。</td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="141">PipedOutputStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="188">任何写入此对象的信息都被放入对应PipedInputStream 对象的缓存中，从而完成线程的通信，实现了“管道”的概念。具体在后面详细讲解。</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="213">利用PipedInputStream构造</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="213">在多线程程序中数据的目的地的。一般将其和FilterOutputStream套接得到额外的功能。</td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="141">FilterOutputStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="188">实现装饰器功能的抽象类。为其它OutputStream对象增加额外的功能。</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="213">见下表</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="213">见下表</td></tr></tbody></table></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       装饰输出字节流：</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><table border="1" cellpadding="0" style="border-collapse: collapse;width:554px;"><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;width:25.992779783393498%;" valign="top" width="143"><strong>类</strong></td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;width:34.47653429602888%;" valign="top" width="190"><strong>功能</strong></td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;width:39.35018050541516%;" valign="top" width="217"><strong>如何构造</strong></td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="217"><strong>怎样使用</strong></td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="143">DataOutputStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="190">通常和DataInputStream配合使用，使用它可以写入基本数据类新。</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="217">使用OutputStream构造</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="217">包含大量的写入基本数据类型的方法。</td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="143">PrintStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="190">产生具有格式的输出信息。（一般地在java程序中DataOutputStream用于数据的存储，即J2EE中持久层完成的功能，PrintStream完成显示的功能，类似于J2EE中表现层的功能）</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="217">使用OutputStream和一个可选的表示缓存是否在每次换行时是否flush的标记构造。还提供很多和文件相关的构造方法。</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="217">一般是一个终极（“final”）的包装器，很多时候我们都使用它！</td></tr><tr><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="143">BufferedOutputStream</td><td rowspan="2" style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="190">使用它可以避免频繁地向IO写入数据，数据一般都写入一个缓存区，在调用flush方法后会清空缓存、一次完成数据的写入。</td><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="217">从一个OutputStream或者和一个代表缓存区大小的可选参数构造。</td></tr><tr><td style="font-style: normal; font-variant: normal; font-weight: normal; font-stretch: normal; font-size: 12px; font-family: 'sans serif', tahoma, verdana, helvetica;" valign="top" width="217">提供和其它OutputStream一致的接口，只是内部提供一个缓存的功能。</td></tr></table></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"> </div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><strong>3.3字节流的输入与输出的对应</strong></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);"><div><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">       在3.1节讲过输入与输出的对应，下图表示字节流部分的输入与输出的对应关系。 </span></span></span></div><div><img src="Java IO_files/Image.png" type="image/png"/></div><div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"> 上图中蓝色的为主要的对应部分，红色的部分就是不对应部分。我习惯上称之为“不入流”部分。紫色的虚线部分代表这些流一般要搭配使用。从上面的图中可以看出Java IO中的字节流是极其对称的。</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">“存在及合理”我们看看这些字节流中不太对称的几个类吧！</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">1.         LineNumberInputStream主要完成从流中读取数据时，会得到相应的行号，至于什么时候分行、在哪里分行是由改类主动确定的，并不是在原始中有这样一个行号。在输出部分没有对应的部分，我们完全可以自己建立一个LineNumberOutputStream，在最初写入时会有一个基准的行号，以后每次遇到换行时会在下一行添加一个行号，看起来也是可以的。好像更不入流了。</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">2.         PushbackInputStream的功能是查看最后一个字节，不满意就放入缓冲区。主要用在编译器的语法、词法分析部分。输出部分的BufferedOutputStream几乎实现相近的功能。</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">3.         StringBufferInputStream已经被Deprecated，本身就不应该出现在InputStream部分，主要因为String应该属于字符流的范围。已经被废弃了，当然输出部分也没有必要需要它了！还允许它存在只是为了保持版本的向下兼容而已。</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">4.         SequenceInputStream可以认为是一个工具类，将两个或者多个输入流当成一个输入流依次读取。完全可以从IO包中去除，还完全不影响IO包的结构，却让其更“纯洁”――纯洁的Decorator模式。</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">5.         PrintStream也可以认为是一个辅助工具。主要可以向其他输出流，或者FileInputStream写入数据，本身内部实现还是带缓冲的。本质上是对其它流的综合运用的一个工具而已。一样可以踢出IO包！System.out和System.out就是PrintStream的实例！</div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">蓝色的部分是IO字节流的主要组成部分，存在极强的对称关系。关于搭配使用的三对类补充一下：ObjectInputStream/ObjectOutputStream和DataInputStream/DataOutputStream主要是要求写对象/数据和读对象/数据的次序要保持一致，否则轻则不能得到正确的数据，重则抛出异常(一般会如此)；PipedInputStream/PipedOutputStream在创建时一般就一起创建，调用它们的读写方法时会检查对方是否存在，或者关闭！道理极其简单――对方都不在了，怎么交互啊！</div><h3 style="font-style: normal; font-variant: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; background-color: rgb(255, 255, 255);"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>3.4 字节流与字符流</h3><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       从上面我们可以看出IO中的字节流是极其复杂的，存在大量的类，到目前为止还没有真正使用它们，使用它们应该也是极其复杂的吧！JDK1.1后Sun对IO库进行了重大的改进。看到Reader和Writer类时，大多数人的第一个感觉（不要太相信感觉哦！感觉也许会欺骗你的！）就是它们是用来替换原来的InputStream和OutputStream类。有新的类，干吗还使用旧的呢！？但实情并非如此。尽管Sun不建议使用原始的流库中的某些功能，但原来的流依然得到了保留，不仅为了保持向后兼容，主要原因是新库不是旧库的替代，而是对旧库的增强。从以下两点可以明显地看出：</p><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">(1) 在老式的类层次结构里加入了新的类，这表明 Sun公司没有放弃老式流库的意图。</p><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">(2) 在许多情况下，新库中类的使用需要联合老结构中的类。为达到这个目的，需要使用一些“桥”类，如：InputStreamReader将一个InputStream转换成Reader；OutputStreamWriter将一个OutputStream转换成Writer。</p><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">那么Sun为什么在Java 1.1里添加了Reader和Writer层次，最重要的原因便是国际化（Internationalization――i18n）的需求。老式IO流层次结构只支持8位字节流，不能很好地控制16位的Unicode字符。Java本身支持Unicode，Sun又一致吹嘘其支持Unicode，因此有必要实现一个支持Unicode的流的层次结构，所以出现了Reader和Writer层次，以提供对所有IO操作中的Unicode的支持。除此之外，新库也对速度进行了优化，可比旧库更快地运行。</p><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">8位的字节流和16位的字符流的对应关系，可以从ByteInputStream/ByteOutputStream与CharArrayInputStream/CharArrayOutputStream的对应关系中看出端倪。（还没看出来啊！赶紧去看看Java的基本数据类型）。</p><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">因此在Java的IO体系中存在字节流和字符流的对应关系。下面就看看字符流吧！</p><h3 style="font-style: normal; font-variant: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; background-color: rgb(255, 255, 255);"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>3.5 IO中的输入字符流</h3><p align="left" style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       下面是IO中输入字符流的继承图。</p><ul style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><li> </li><li style="list-style: none; display: inline"><ul><li><strong>Reader</strong></li></ul></li></ul><ul style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><li> </li><li style="list-style: none; display: inline"><ul><li> </li><li style="list-style: none; display: inline"><ul><li><strong>BufferedReader</strong></li></ul></li></ul></li></ul><ul style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><li> </li><li style="list-style: none; display: inline"><ul><li> </li><li style="list-style: none; display: inline"><ul><li> </li><li style="list-style: none; display: inline"><ul><li><strong>LineNumberReader</strong></li></ul></li><li><strong>CharArrayReader</strong></li><li><strong>FilterReader</strong></li><li style="list-style: none; display: inline"><ul><li><strong>PushbackReader</strong></li></ul></li><li><strong>InputStreamReader</strong></li><li style="list-style: none; display: inline"><ul><li><strong>FileReader</strong></li></ul></li><li><strong>PipedReader</strong></li><li><strong>StringReader</strong></li></ul></li></ul></li></ul><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">在上面的关系图中可以看出：1.Reader是所有的输入字符流的父类，它是一个抽象类。2.CharReader、StringReader是两种基本的介质流，它们分别将Char数组、String中读取数据。PipedReader是从与其它线程共用的管道中读取数据。3. BufferedReader很明显就是一个装饰器，它和其子类负责装饰其它Reader对象。4.FilterReader是所有自定义具体装饰流的父类，其子类PushbackReader对Reader对象进行装饰，会增加一个行号。5.InputStreamReader是一个连接字节流和字符流的桥梁，它将字节流转变为字符流。FileReader可以说是一个达到此功能、常用的工具类，在其源代码中明显使用了将FileInputStream转变为Reader的方法。我们可以从这个类中得到一定的技巧。</p><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       Reader中各个类的用途和使用方法基本和InputStream中的类使用一致。后面会有Reader与InputStream的对应关系。</p><h3 style="font-style: normal; font-variant: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; background-color: rgb(255, 255, 255);"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>3.6 IO中的输出字符流</h3><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">下面是IO中输出字符流的继承图。</p><ul style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><li> </li><li style="list-style: none; display: inline"><ul><li><strong>Writer</strong></li></ul></li></ul><ul style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><li> </li><li style="list-style: none; display: inline"><ul><li> </li><li style="list-style: none; display: inline"><ul><li><strong>BufferedWriter</strong></li><li><strong>CharArrayWriter</strong></li><li><strong>FilterWriter</strong></li><li><strong>OutputStreamWriter</strong></li></ul></li></ul></li></ul><ul style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><li> </li><li style="list-style: none; display: inline"><ul><li> </li><li style="list-style: none; display: inline"><ul><li> </li><li style="list-style: none; display: inline"><ul><li><strong>FileWriter</strong></li></ul></li><li><strong>PipedWriter</strong></li><li><strong>PrintWriter</strong></li><li><strong>StringWriter</strong></li></ul></li></ul></li></ul><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">在上面的关系图中可以看出：1.Writer是所有的输出字符流的父类，它是一个抽象类。2. CharArrayWriter、StringWriter是两种基本的介质流，它们分别向Char数组、String中写入数据。PipedWriter是向与其它线程共用的管道中写入数据， 3. BufferedWriter是一个装饰器为Writer提供缓冲功能。4.PrintWriter和PrintStream极其类似，功能和使用也非常相似。5.OutputStreamWriter是OutputStream到Writer转换的桥梁，它的子类FileWriter其实就是一个实现此功能的具体类（具体可以研究一下Source Code）。功能和使用和OutputStream极其类似，后面会有它们的对应图。</p><h3 style="font-style: normal; font-variant: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; background-color: rgb(255, 255, 255);"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>3.7字符流的输入与输出的对应</h3><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">下图为字符流的输入与输出的对应关系图：</p></div><div><img src="Java IO_files/Image [1].png" type="image/png"/></div><div><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"> 对应关系和字节流的输入输出基本一致，不必多说了吧！在下面的源代码阅读部分会仔细研究一些！</p><h3 style="font-style: normal; font-variant: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; background-color: rgb(255, 255, 255);"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>3.8字节流和字符流的对应</h3><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);">       Java的IO中存在输入、输出的对应和字节流和字符流的对应，下面就看看字节流和字符流的对应吧！</p><h4 style="font-style: normal; font-variant: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>3.8.1输入的对应</h4><div style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);"><div><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">       下图是IO中字节输入流与字符输入流的对应图：</span></span></span></div><div><img src="Java IO_files/Image [2].png" type="image/png"/></div><div><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><br/>
       蓝色的表示对应的部分，红色的表示不对应的部分。至于为什么不对应还是你自己多看看源代码、多考虑考虑吧！还要强调一点就是即使对应，它们的继承关系也是不太对应的。</p><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"> </p><h4 style="font-style: normal; font-variant: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>3.8.2输出的对应</h4><div style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);"><div><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">下图是IO中字节输出流与字符输出流的对应图：</span></span></span></div><div><img src="Java IO_files/Image [3].png" type="image/png"/></div><div><br/></div><div><p style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"> 不多说了！等讲述了Adapter和Decorator模式会基本明白IO架构的！通过几个实例一般就可以使用了！</p><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);"><h1><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>从InputStream到ByteArrayInputStream</span></span></span></h1><p align="right" style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"><strong>       </strong><strong>江苏</strong><strong> </strong><strong>无锡</strong><strong> </strong><strong>缪小东</strong></span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">本篇主要分析：1.如何将byte数组适配至ByteArrayInputStream，对应与IO部分的适配器模式；2.BufferedInputStream的工作原理，对应于IO的装饰器模式，会首先研究InputStream和FilterInputStream的源代码，同时会将要谈谈软件设计中的缓存相关的知识。后面专门一章分析PipedInputStream和PipedOutStream，简单谈谈管道相关的知识，以及软件架构的想法。</span></span></span></p><h3><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>1 InputStream</span></span></span></h3><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">InputStream 是输入字节流部分，装饰器模式的顶层类。主要规定了输入字节流的公共方法。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">package java.io;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">public abstract class InputStream implements Closeable {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    private static final int SKIP_BUFFER_SIZE = 2048;  //用于skip方法，和skipBuffer相关</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    private static byte[] skipBuffer;    // skipBuffer is initialized in skip(long), if needed.</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">public abstract int read() throws IOException;  //从输入流中读取下一个字节，</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                                                                                             //正常返回0-255，到达文件的末尾返回-1</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                                                        //在流中还有数据，但是没有读到时该方法会阻塞（block）</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                                                        //Java IO和New IO的区别就是阻塞流和非阻塞流</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                                                        //抽象方法哦！不同的子类不同的实现哦！</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //将流中的数据读入放在byte数组的第off个位置先后的len个位置中</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //放回值为放入字节的个数。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public int read(byte b[], int off, int len) throws IOException {           //</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (b == null) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             throw new NullPointerException();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         } else if (off &lt; 0 || len &lt; 0 || len &gt; b.length - off) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             throw new IndexOutOfBoundsException();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         } else if (len == 0) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             return 0;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         }        //检查输入是否正常。一般情况下，检查输入是方法设计的第一步</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         int c = read();                                                              //读取下一个字节</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (c == -1) {    return -1;   }                           //到达文件的末端返回-1</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         b[off] = (byte)c;                                                   //放回的字节downcast</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         int i = 1;                                                                        //已经读取了一个字节</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         try {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             for (; i &lt; len ; i++) {                          //最多读取len个字节，所以要循环len次</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   c = read();                                       //每次循环从流中读取一个字节</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                                                                                    //由于read方法阻塞，</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//所以read(byte[],int,int)也会阻塞</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   if (c == -1) {            break;           }       //到达末尾，理所当然放回-1</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   b[off + i] = (byte)c;                                    //读到就放入byte数组中</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         } catch (IOException ee) {     }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         return i;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //上面这个部分其实还有一点比较重要，int i = 1;在循环的外围，或许你经常见到，</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //或许你只会在循环是才声明，为什么呢？</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //声明在外面，增大了变量的生存周期（在循环外面），所以后面可以return返回</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //极其一般的想法。在类成员变量生命周期中使用同样的理念。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //在软件设计中，类和类的关系中也是一样的。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }        //这个方法在利用抽象方法read，某种意义上简单的Templete模式。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public int read(byte b[]) throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   return read(b, 0, b.length);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }                           //利用上面的方法read(byte[] b)</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public long skip(long n) throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         long remaining = n;                                  //方法内部使用的、表示要跳过的字节数目，</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//使用它完成一系列字节读取的循环</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         int nr;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (skipBuffer == null)</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             skipBuffer = new byte[SKIP_BUFFER_SIZE];                   //初始化一个跳转的缓存</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         byte[] localSkipBuffer = skipBuffer;                                      //本地化的跳转缓存</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (n &lt;= 0) {    return 0;      }                           //检查输入参数，应该放在方法的开始</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         while (remaining &gt; 0) {                                      //一共要跳过n个，每次跳过部分，循环</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             nr = read(localSkipBuffer, 0, (int) Math.min(SKIP_BUFFER_SIZE, remaining));</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                                                        //利用上面的read(byte[],int,int)方法尽量读取n个字节  </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             if (nr &lt; 0) {  break;    }                          //读到流的末端，则返回</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             remaining -= nr;                                       //没有完全读到需要的，则继续循环</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         }       </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         return n - remaining;//返回时要么全部读完，要么因为到达文件末端，读取了部分</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public int available() throws IOException {                  //查询流中还有多少可以读取的字节</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   return 0;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //该方法不会block。在java中抽象类方法的实现一般有以下几种方式：</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//1.抛出异常（java.util）；2.“弱”实现。象上面这种。子类在必要的时候覆盖它。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//3.“空”实现。下面有例子。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public void close() throws IOException {}</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //关闭当前流、同时释放与此流相关的资源</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized void mark(int readlimit) {}</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //在当前位置对流进行标记，必要的时候可以使用reset方法返回。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //markSupport可以查询当前流是否支持mark</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized void reset() throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   throw new IOException(&quot;mark/reset not supported&quot;);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //对mark过的流进行复位。只有当流支持mark时才可以使用此方法。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //看看mark、available和reset方法。体会为什么？！</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public boolean markSupported() {           //查询是否支持mark</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   return false;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }                 //绝大部分不支持，因此提供默认实现，返回false。子类有需要可以覆盖。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">}</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><h3><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>2 FilterInputStream</span></span></span></h3><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">       这是字节输入流部分装饰器模式的核心。是我们在装饰器模式中的Decorator对象，主要完成对其它流装饰的基本功能。下面是它的源代码:</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">package java.io;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//该类对被装饰的流进行基本的包裹。不增加额外的功能。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//客户在需要的时候可以覆盖相应的方法。具体覆盖可以在ByteInputStream中看到！</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">public class FilterInputStream extends InputStream {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    protected volatile InputStream in;                       //将要被装饰的字节输入流</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    protected FilterInputStream(InputStream in) {   //通过构造方法传入此被装饰的流</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   this.in = in;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //装饰器的代码特征：被装饰的对象一般是装饰器的成员变量</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //上面几行可以看出。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //下面这些方法，完成最小的装饰――0装饰，只是调用被装饰流的方法而已</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public int read() throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   return in.read();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public int read(byte b[]) throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   return read(b, 0, b.length);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public int read(byte b[], int off, int len) throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   return in.read(b, off, len);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public long skip(long n) throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   return in.skip(n);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public int available() throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   return in.available();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public void close() throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   in.close();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized void mark(int readlimit) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   in.mark(readlimit);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized void reset() throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   in.reset();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public boolean markSupported() {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   return in.markSupported();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">}</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//以上的方法，都是通过调用被装饰对象in完成的。没有添加任何额外功能</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//装饰器模式中的Decorator对象，不增加被装饰对象的功能。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//它是装饰器模式中的核心。更多关于装饰器模式的理论请阅读博客中的文章。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">}</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">       以上分析了所有字节输入流的公共父类InputStream和装饰器类FilterInputStream类。他们是装饰器模式中两个重要的类。更多细节请阅读博客中装饰器模式的文章。下面将讲解一个具体的流ByteArrayInputStream，不过它是采用适配器设计模式。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><h3><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>3 ByteArray到ByteArrayInputStream的适配</span></span></span></h3><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">// ByteArrayInputStream内部有一个byte类型的buffer。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//很典型的适配器模式的应用――将byte数组适配流的接口。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//下面是源代码分析：</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">package java.io;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">public class ByteArrayInputStream extends InputStream {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    protected byte buf[];                //内部的buffer，一般通过构造器输入</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">protected int pos;                   //当前位置的cursor。从0至byte数组的长度。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//byte[pos]就是read方法读取的字节</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    protected int mark = 0;           //mark的位置。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    protected int count;                          //流中字节的数目。不一定与byte[]的长度一致？？？</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public ByteArrayInputStream(byte buf[]) {//从一个byte[]创建一个ByteArrayInputStream</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         this.buf = buf;                                                      //初始化流中的各个成员变量</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        this.pos = 0;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         this.count = buf.length;                              //count就等于buf.length</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public ByteArrayInputStream(byte buf[], int offset, int length) {                //构造器</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         this.buf = buf;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        this.pos = offset;                                                                                      //与上面不同</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         this.count = Math.min(offset + length, buf.length);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        this.mark = offset;                                                                                             //与上面不同</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized int read() {                                           //从流中读取下一个字节</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   return (pos &lt; count) ? (buf[pos++] &amp; 0xff) : -1; //返回下一个位置的字节</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                                                                                                                //流中没有数据则返回-1</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //下面这个方法很有意思！从InputStream中可以看出其提供了该方法的实现。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //为什么ByteArrayInputStream要覆盖此方法呢？</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //同样的我们在Java Collections Framework中可以看到：</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//AbstractCollection利用iterator实现了Collecion接口的很多方法。但是，</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//在ArrayList中却有很多被子类覆盖了。为什么如此呢？？</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized int read(byte b[], int off, int len) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (b == null) {                                                               //首先检查输入参数的状态是否正确</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             throw new NullPointerException();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         } else if (off &lt; 0 || len &lt; 0 || len &gt; b.length - off) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             throw new IndexOutOfBoundsException();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (pos &gt;= count) {             return -1;             }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (pos + len &gt; count) {      len = count - pos;         }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (len &lt;= 0) {           return 0;     }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         System.arraycopy(buf, pos, b, off, len);                     //java中提供数据复制的方法</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         pos += len;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         return len;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //出于速度的原因！他们都用到System.arraycopy方法。想想为什么？</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //某些时候，父类不能完全实现子类的功能，父类的实现一般比较通用。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//当子类有更有效的方法时，我们会覆盖这些方法。这样可是不太OO的哦！</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //下面这个方法，在InputStream中也已经实现了。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//但是当时是通过将字节读入一个buffer中实现的，好像效率低了一点。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//看看下面这段代码，是否极其简单呢？！</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized long skip(long n) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (pos + n &gt; count) {    n = count - pos;       }        //当前位置，可以跳跃的字节数目</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (n &lt; 0) {       return 0;     }                                    //小于0，则不可以跳跃</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         pos += n;                                                                              //跳跃后，当前位置变化</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         return n;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }                                    //比InputStream中的方法简单、高效吧！</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized int available() {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   return count - pos;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //查询流中还有多少字节没有读取。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//在我们的ByteArrayInputStream中就是当前位置以后字节的数目。  </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public boolean markSupported() {                   </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   return true;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }        //ByteArrayInputStream支持mark所以返回true</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public void mark(int readAheadLimit) {            </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   mark = pos;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//在流中当前位置mark。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//在我们的ByteArrayInputStream中就是将当前位置赋给mark变量。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//读取流中的字节就是读取字节数组中当前位置向后的的字节。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized void reset() {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   pos = mark;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //重置流。即回到mark的位置。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public void close() throws IOException {   }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //关闭ByteArrayInputStream不会产生任何动作。为什么？仔细考虑吧！！</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">}</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">上面我们分3小节讲了装饰器模式中的公共父类（对应于输入字节流的InputStream）、Decorator（对应于输入字节流的FilterInputStream）和基本被装饰对象（对应于输入字节流的媒体字节流）。下面我们就要讲述装饰器模式中的具体的包装器（对应于输入字节流的包装器流）。</span></span></span></p><h3><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>4 BufferedInputStream</span></span></span></h3><h4><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>4.1原理及其在软件硬件中的应用</span></span></span></h4><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">       1.read――read(byte[] ,int , int)</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">       2.BufferedInputStream</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">       3.《由一个简单的程序谈起》</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">       4. Cache</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">       5.Pool</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">       6.Spling Printer</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">       （最近比较忙，不讲了！）</span></span></span></p><h4><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>4.2 BufferedInputStream源代码分析</span></span></span></h4><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">package java.io;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//该类主要完成对被包装流，加上一个缓存的功能</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">public class BufferedInputStream extends FilterInputStream {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    private static int defaultBufferSize = 8192;                                      //默认缓存的大小</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    protected volatile byte buf[];                                                            //内部的缓存</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    protected int count;                                                                                            //buffer的大小</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    protected int pos;                                                                               //buffer中cursor的位置</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    protected int markpos = -1;                                                                     //mark的位置</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    protected int marklimit;                                                                            //mark的范围</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//原子性更新。和一致性编程相关</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    private static final</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        AtomicReferenceFieldUpdater&lt;BufferedInputStream, byte[]&gt; bufUpdater =</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        AtomicReferenceFieldUpdater.newUpdater (BufferedInputStream.class,  byte[].class, &quot;buf&quot;);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    private InputStream getInIfOpen() throws IOException {  //检查输入流是否关闭，同时返回被包装流</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        InputStream input = in;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (input == null)    throw new IOException(&quot;Stream closed&quot;);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        return input;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    private byte[] getBufIfOpen() throws IOException {                       //检查buffer的状态，同时返回缓存</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        byte[] buffer = buf;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (buffer == null)   throw new IOException(&quot;Stream closed&quot;);            //不太可能发生的状态</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        return buffer;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public BufferedInputStream(InputStream in) {                               //构造器</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   this(in, defaultBufferSize);                                                              //指定默认长度的buffer</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public BufferedInputStream(InputStream in, int size) {                           //构造器</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   super(in);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        if (size &lt;= 0) {                                                                                         //检查输入参数</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            throw new IllegalArgumentException(&quot;Buffer size &lt;= 0&quot;);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   buf = new byte[size];                                                                     //创建指定长度的buffer</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //从流中读取数据，填充如缓存中。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    private void fill() throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        byte[] buffer = getBufIfOpen();                            //得到buffer</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (markpos &lt; 0)</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             pos = 0;                                                             //mark位置小于0，此时pos为0</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         else if (pos &gt;= buffer.length)                               //pos大于buffer的长度</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             if (markpos &gt; 0) {        </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   int sz = pos - markpos;                            //</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   System.arraycopy(buffer, markpos, buffer, 0, sz);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   pos = sz;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   markpos = 0;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             } else if (buffer.length &gt;= marklimit) {                 //buffer的长度大于marklimit时，mark失效</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   markpos = -1;                                                   //</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   pos = 0;                                                             //丢弃buffer中的内容</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             } else {                                                                         //buffer的长度小于marklimit时对buffer扩容</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   int nsz = pos * 2;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   if (nsz &gt; marklimit)           nsz = marklimit;//扩容为原来的2倍，太大则为marklimit大小</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   byte nbuf[] = new byte[nsz];                    </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   System.arraycopy(buffer, 0, nbuf, 0, pos);        //将buffer中的字节拷贝如扩容后的buf中</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                if (!bufUpdater.compareAndSet(this, buffer, nbuf)) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                                                                                                                         //在buffer在被操作时，不能取代此buffer</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                    throw new IOException(&quot;Stream closed&quot;);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                buffer = nbuf;                                                               //将新buf赋值给buffer</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        count = pos;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         int n = getInIfOpen().read(buffer, pos, buffer.length - pos);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        if (n &gt; 0)     count = n + pos;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized int read() throws IOException { //读取下一个字节</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (pos &gt;= count) {                                                                 //到达buffer的末端</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             fill();                                                                    //就从流中读取数据，填充buffer</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             if (pos &gt;= count)  return -1;                                //读过一次，没有数据则返回-1</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         return getBufIfOpen()[pos++] &amp; 0xff;                           //返回buffer中下一个位置的字节</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    private int read1(byte[] b, int off, int len) throws IOException {                 //将数据从流中读入buffer中</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         int avail = count - pos;                                                                             //buffer中还剩的可读字符</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (avail &lt;= 0) {                                                                                        //buffer中没有可以读取的数据时</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             if (len &gt;= getBufIfOpen().length &amp;&amp; markpos &lt; 0) {             //将输入流中的字节读入b中</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   return getInIfOpen().read(b, off, len);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             fill();                                                                                                //填充</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             avail = count - pos;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             if (avail &lt;= 0) return -1;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         int cnt = (avail &lt; len) ? avail : len;                                                  //从流中读取后，检查可以读取的数目</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         System.arraycopy(getBufIfOpen(), pos, b, off, cnt);            //将当前buffer中的字节放入b的末端</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         pos += cnt;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         return cnt;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized int read(byte b[], int off, int len)throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        getBufIfOpen();                                                                             // 检查buffer是否open</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        if ((off | len | (off + len) | (b.length - (off + len))) &lt; 0) {            //检查输入参数是否正确</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             throw new IndexOutOfBoundsException();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         } else if (len == 0) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            return 0;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         int n = 0;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        for (;;) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            int nread = read1(b, off + n, len - n);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            if (nread &lt;= 0)     return (n == 0) ? nread : n;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            n += nread;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            if (n &gt;= len)     return n;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            // if not closed but no bytes available, return</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            InputStream input = in;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            if (input != null &amp;&amp; input.available() &lt;= 0)     return n;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized long skip(long n) throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        getBufIfOpen();                                        // 检查buffer是否关闭</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (n &lt;= 0) {    return 0;      }                 //检查输入参数是否正确</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         long avail = count - pos;                    //buffered中可以读取字节的数目</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        if (avail &lt;= 0) {                                          //可以读取的小于0，则从流中读取</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            if (markpos &lt;0)  return getInIfOpen().skip(n); //mark小于0，则mark在流中      </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            fill();                                  // 从流中读取数据，填充缓冲区。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            avail = count - pos;                                   //可以读的取字节为buffer的容量减当前位置</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            if (avail &lt;= 0)     return 0;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        }       </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        long skipped = (avail &lt; n) ? avail : n;      </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        pos += skipped;                                       //当前位置改变</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        return skipped;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized int available() throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   return getInIfOpen().available() + (count - pos);                 </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //该方法不会block！返回流中可以读取的字节的数目。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //该方法的返回值为缓存中的可读字节数目加流中可读字节数目的和</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized void mark(int readlimit) {  //当前位置处为mark位置</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         marklimit = readlimit;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         markpos = pos;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized void reset() throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        getBufIfOpen(); // 缓冲去关闭了，肯定就抛出异常！程序设计中经常的手段</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   if (markpos &lt; 0)     throw new IOException(&quot;Resetting to invalid mark&quot;);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   pos = markpos;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public boolean markSupported() {           //该流和ByteArrayInputStream一样都支持mark</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   return true;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         //关闭当前流同时释放相应的系统资源。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public void close() throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        byte[] buffer;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        while ( (buffer = buf) != null) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            if (bufUpdater.compareAndSet(this, buffer, null)) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                InputStream input = in;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                in = null;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                if (input != null)    input.close();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                return;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            // Else retry in case a new buf was CASed in fill()</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">}</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><h1><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>从PipedInputStream/PipedOutputStream谈起</span></span></span></h1><p align="right" style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">       江苏 无锡 缪小东</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">本篇主要从分析PipeInputStrem和PipedOutputStream谈起。谈及软件设计的变化，以及如何将软件拆分、组合，适配……</span></span></span></p><h3><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>1 源代码分析</span></span></span></h3><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">       下面将详细分析PipedInputStream和PipedOutputStream的源代码。</span></span></span></p><h4><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>1.1 PipedInputStream</span></span></span></h4><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">package java.io;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//PipedInputStream必须和PipedOutputStream联合使用。即必须连接输入部分。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//其原理为：PipedInputStream内部有一个Buffer，</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//PipedInputStream可以使用InputStream的方法读取其Buffer中的字节。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//PipedInputStream中Buffer中的字节是PipedOutputStream调用PipedInputStream的方法放入的。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">public class PipedInputStream extends InputStream {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    boolean closedByWriter = false;                                                             //标识有读取方或写入方关闭</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    volatile boolean closedByReader = false;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    boolean connected = false;                                                                     //是否建立连接</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    Thread readSide;                                                                                             //标识哪个线程</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    Thread writeSide;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    protected static final int PIPE_SIZE = 1024;                         //缓冲区的默认大小</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    protected byte buffer[] = new byte[PIPE_SIZE];                  //缓冲区</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    protected int in = -1;               //下一个写入字节的位置。0代表空，in==out代表满</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    protected int out = 0;               //下一个读取字节的位置</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public PipedInputStream(PipedOutputStream src) throws IOException {                //给定源的输入流</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   connect(src);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public PipedInputStream() {    }                                                //默认构造器，下部一定要connect源</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public void connect(PipedOutputStream src) throws IOException {               //连接输入源</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   src.connect(this);                                                                           //调用源的connect方法连接当前对象</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    protected synchronized void receive(int b) throws IOException {                   //只被PipedOuputStream调用</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        checkStateForReceive();                                                                                 //检查状态，写入</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        writeSide = Thread.currentThread();                                                      //永远是PipedOuputStream</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        if (in == out)     awaitSpace();                                                           //输入和输出相等，等待空间</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (in &lt; 0) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             in = 0;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             out = 0;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         buffer[in++] = (byte)(b &amp; 0xFF);                                                             //放入buffer相应的位置</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (in &gt;= buffer.length) {      in = 0;         }                                             //in为0表示buffer已空</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    synchronized void receive(byte b[], int off, int len)  throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        checkStateForReceive();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        writeSide = Thread.currentThread();                                   //从PipedOutputStream可以看出</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        int bytesToTransfer = len;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        while (bytesToTransfer &gt; 0) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            if (in == out)    awaitSpace();                                 //满了，会通知读取的；空会通知写入</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            int nextTransferAmount = 0;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            if (out &lt; in) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                nextTransferAmount = buffer.length - in;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            } else if (in &lt; out) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                if (in == -1) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                    in = out = 0;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                    nextTransferAmount = buffer.length - in;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                } else {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                    nextTransferAmount = out - in;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            if (nextTransferAmount &gt; bytesToTransfer)     nextTransferAmount = bytesToTransfer;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            assert(nextTransferAmount &gt; 0);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            System.arraycopy(b, off, buffer, in, nextTransferAmount);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            bytesToTransfer -= nextTransferAmount;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            off += nextTransferAmount;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            in += nextTransferAmount;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            if (in &gt;= buffer.length) {     in = 0;      }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    private void checkStateForReceive() throws IOException {                           //检查当前状态，等待输入</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        if (!connected) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            throw new IOException(&quot;Pipe not connected&quot;);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        } else if (closedByWriter || closedByReader) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             throw new IOException(&quot;Pipe closed&quot;);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         } else if (readSide != null &amp;&amp; !readSide.isAlive()) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            throw new IOException(&quot;Read end dead&quot;);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    private void awaitSpace() throws IOException {                                              //Buffer已满，等待一段时间</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         while (in == out) {                                                                                             //in==out表示满了，没有空间</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             checkStateForReceive();                                                                       //检查接受端的状态</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             notifyAll();                                                                                  //通知读取端</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             try {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                 wait(1000);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             } catch (InterruptedException ex) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   throw new java.io.InterruptedIOException();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    synchronized void receivedLast() {                  //通知所有等待的线程（）已经接受到最后的字节</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         closedByWriter = true;                             //</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         notifyAll();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized int read()  throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        if (!connected) {                                                                              //检查一些内部状态</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            throw new IOException(&quot;Pipe not connected&quot;);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        } else if (closedByReader) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             throw new IOException(&quot;Pipe closed&quot;);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         } else if (writeSide != null &amp;&amp; !writeSide.isAlive()&amp;&amp; !closedByWriter &amp;&amp; (in &lt; 0)) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            throw new IOException(&quot;Write end dead&quot;);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        readSide = Thread.currentThread();                                            //当前线程读取</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         int trials = 2;                                                                                             //重复两次？？？？</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         while (in &lt; 0) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             if (closedByWriter) {              return -1;        }                 //输入断关闭返回-1</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             if ((writeSide != null) &amp;&amp; (!writeSide.isAlive()) &amp;&amp; (--trials &lt; 0)) {          //状态错误</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   throw new IOException(&quot;Pipe broken&quot;);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             notifyAll();                                                             // 空了，通知写入端可以写入</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             try {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                 wait(1000);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             } catch (InterruptedException ex) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   throw new java.io.InterruptedIOException();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         int ret = buffer[out++] &amp; 0xFF;                                                        //</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (out &gt;= buffer.length) {             out = 0;                }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (in == out) {           in = -1;                 }                             //没有任何字节</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         return ret;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized int read(byte b[], int off, int len)  throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">     if (b == null) {                                                                                 //检查输入参数的正确性</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         throw new NullPointerException();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">     } else if (off &lt; 0 || len &lt; 0 || len &gt; b.length - off) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         throw new IndexOutOfBoundsException();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">     } else if (len == 0) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         return 0;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">     }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">     int c = read();                                                                                 //读取下一个</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">     if (c &lt; 0) {    return -1;       }                                             //已经到达末尾了，返回-1</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">     b[off] = (byte) c;                                                                    //放入外部buffer中</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">     int rlen = 1;                                                                            //return-len</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">     while ((in &gt;= 0) &amp;&amp; (--len &gt; 0)) {                                          //下一个in存在，且没有到达len</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         b[off + rlen] = buffer[out++];                                         //依次放入外部buffer</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         rlen++;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (out &gt;= buffer.length) {         out = 0;           }        //读到buffer的末尾，返回头部</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (in == out) {     in = -1;      }               //读、写位置一致时，表示没有数据</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">     }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">     return rlen;                                                                            //返回填充的长度</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized int available() throws IOException {             //返回还有多少字节可以读取</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if(in &lt; 0)</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             return 0;                                                                                         //到达末端，没有字节</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         else if(in == out)</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             return buffer.length;                                                               //写入的和读出的一致，表示满</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         else if (in &gt; out)</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             return in - out;                                                                                 //写入的大于读出</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         else</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             return in + buffer.length - out;                                                //写入的小于读出的</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public void close()  throws IOException {                //关闭当前流，同时释放与其相关的资源</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         closedByReader = true;                                             //表示由输入流关闭</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        synchronized (this) {     in = -1;    }        //同步化当前对象，in为-1</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">}</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><h4><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>1.2 PipedOutputStream</span></span></span></h4><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">// PipedOutputStream一般必须和一个PipedInputStream连接。共同构成一个pipe。</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">//它们的职能是：</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">package java.io;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">import java.io.*;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">public class PipedOutputStream extends OutputStream {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    private PipedInputStream sink;                //包含一个PipedInputStream</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public PipedOutputStream(PipedInputStream snk)throws IOException {       //带有目的地的构造器</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">                   connect(snk);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">   </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public PipedOutputStream() {  }                      //默认构造器，必须使用下面的connect方法连接</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">   </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized void connect(PipedInputStream snk) throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        if (snk == null) {                                                                    //检查输入参数的正确性</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            throw new NullPointerException();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        } else if (sink != null || snk.connected) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             throw new IOException(&quot;Already connected&quot;);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         sink = snk;                                                                           //一系列初始化工作</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         snk.in = -1;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         snk.out = 0;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        snk.connected = true;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public void write(int b) throws IOException {                        //向流中写入数据</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        if (sink == null) {    throw new IOException(&quot;Pipe not connected&quot;);      }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         sink.receive(b);            //本质上是，调用PipedInputStream的receive方法接受此字节</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public void write(byte b[], int off, int len) throws IOException {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        if (sink == null) {                                                                   //首先检查输入参数的正确性</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            throw new IOException(&quot;Pipe not connected&quot;);</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">        } else if (b == null) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             throw new NullPointerException();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         } else if ((off &lt; 0) || (off &gt; b.length) || (len &lt; 0) || ((off + len) &gt; b.length) || ((off + len) &lt; 0)) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             throw new IndexOutOfBoundsException();</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         } else if (len == 0) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">             return;</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         sink.receive(b, off, len);                                                                 //调用PipedInputStream的receive方法接受</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public synchronized void flush() throws IOException {                 //flush输出流</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (sink != null) {</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">            synchronized (sink) {     sink.notifyAll();     } //本质是通知输入流，可以读取</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    public void close()  throws IOException {                         //关闭流同时释放相关资源</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">         if (sink != null) {    sink.receivedLast();         }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">    }</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;">}</span></span></span></p><p style="word-wrap: break-word; margin: 5px 0px;"><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span></p><div><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"><br/></span></span></span></div><div style="font-weight: bold; font-size: 16px;"><span style="color: rgb(51, 51, 51);"><span style="font-family: Arial;"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>2 Buffer的状态</span></span></div><div><img src="Java IO_files/Image [4].png" type="image/png"/></div><div><p align="center" style="word-wrap: break-word; margin: 5px 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);"> </p><p style="word-wrap: break-word; margin: 5px 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);">       上图是PipedInputStream中缓存的状态图。在程序中我们利用了byte数组，循环地向其中写入数据，写入有一个cursor（in），读出也有一个cursor（out）。上图表示in和out不同位置时，buffer中的各个位置的状态。蓝色的代表可以读取的字节。白色的表示此位置没有字节，或者此位置已经被PipedInputStream读取了。</p><h3 style="color: rgb(51, 51, 51); font-family: Arial; font-style: normal; font-variant: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);"><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>3 交互简图</h3><p style="word-wrap: break-word; margin: 5px 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);">       下图是从源代码部分转换过来的关于PipedInputStream和PipedOutputStream的交互图。</p><div style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);"><div><span style="color: rgb(51, 51, 51);"><span style="font-size: 14px;"><span style="font-family: Arial;"> </span></span></span><img src="Java IO_files/Image [5].png" type="image/png"/></div><div style="word-wrap: break-word; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; font-size: 14px; background-color: rgb(255, 255, 255);"><p style="word-wrap: break-word; margin: 5px 0px;">       从图中可以看出：</p><p style="word-wrap: break-word; margin: 5px 0px;">1.         整个PipedInputStream是这对管道的核心。管道本身是一个byte的数组。</p><p style="word-wrap: break-word; margin: 5px 0px;">2.         PipedOutputStream对象通过Delegate方法复用PipedInputStream，同时屏蔽了其中的读取的方法，我们仅仅可以构造PipedOutputStream对象。（从这一点可以看出Delegate复用比继承复用的优越性了！）从设计模式的角度更象Adapter――PipedInputStream本身提供读取和写入的功能，将写入的功能适配到OutputStream，就成为一个PipedOutputStream。这样就形成一个类，适配后形成两种功能的类。</p><p style="word-wrap: break-word; margin: 5px 0px;">3.         调用PipedOutputStream的连接方法实际就是调用PipedInputStream的连接方法。</p><p style="word-wrap: break-word; margin: 5px 0px;">4.         调用PipedOutputStream的写相关的方法实际就是调用PipedInputStream的对应方法。</p><p style="word-wrap: break-word; margin: 5px 0px;">以上也是一种适配，将管道的概念适配到流的概念，同时将两者的职能分开。</p><p style="word-wrap: break-word; margin: 5px 0px;"> </p><h3><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>4 将Chanel放入PipedOutputStream</h3><p style="word-wrap: break-word; margin: 5px 0px;">       上面的例子中，Chanel放在PipedInputStream中，我们仔细思考后可以顺理成章地将其Chanel放入PipedOutputStream中。请注意synchronized方法是得到哪个字节流的锁！！</p><h3><img src="http://blog.n8n.cn/wp-content/plugins/kindeditor-for-wordpress/themes/common/anchor.gif" style="border: 1px dashed rgb(102, 102, 102); width: 16px; height: 16px;"></img>5 Chanel移出的一个例子</h3><p style="word-wrap: break-word; margin: 5px 0px;">       在上面两个例子中Buffer要么在写入对象的内部，要么在读取对象的内部。主要通过适配该对象的方法，达到自己的需求而已。下面是一个一般的例子――将Chanel移出，Chanel提供了写入与读取的功能。这也完全合乎OO的“Single Responsibility Protocol――SRP”。输入部分使用Delegate复用此Chanel，将其适配至InputStream和OutputStream。下面是简单的Source code。</p><p style="word-wrap: break-word; margin: 5px 0px;">//PipedChanel.java</p><p style="word-wrap: break-word; margin: 5px 0px;">       import java.io.IOException ;</p><p style="word-wrap: break-word; margin: 5px 0px;"> </p><p style="word-wrap: break-word; margin: 5px 0px;">public class PipedChanel {</p><p style="word-wrap: break-word; margin: 5px 0px;">    protected static final int PIPE_SIZE = 1024;</p><p style="word-wrap: break-word; margin: 5px 0px;">    protected byte buffer[] = new byte[PIPE_SIZE];   </p><p style="word-wrap: break-word; margin: 5px 0px;">    protected int in = -1;</p><p style="word-wrap: break-word; margin: 5px 0px;">protected int out = 0;</p><p style="word-wrap: break-word; margin: 5px 0px;">   </p><p style="word-wrap: break-word; margin: 5px 0px;">    public PipedChanel(){  }       </p><p style="word-wrap: break-word; margin: 5px 0px;">    public PipedChanel(int size){</p><p style="word-wrap: break-word; margin: 5px 0px;">           buffer = new byte[size]  ; </p><p style="word-wrap: break-word; margin: 5px 0px;">    }   </p><p style="word-wrap: break-word; margin: 5px 0px;">   </p><p style="word-wrap: break-word; margin: 5px 0px;">    public synchronized int read() throws IOException {    }       </p><p style="word-wrap: break-word; margin: 5px 0px;">    public synchronized int read(byte b[], int off, int len)  throws IOException {    }   </p><p style="word-wrap: break-word; margin: 5px 0px;">    public synchronized int available() throws IOException {}   </p><p style="word-wrap: break-word; margin: 5px 0px;">    public synchronized void close()  throws IOException {}       </p><p style="word-wrap: break-word; margin: 5px 0px;">   </p><p style="word-wrap: break-word; margin: 5px 0px;">public synchronized void write(int b)  throws IOException {}</p><p style="word-wrap: break-word; margin: 5px 0px;">public synchronized void write(byte b[]) throws IOException {}</p><p style="word-wrap: break-word; margin: 5px 0px;">    public synchronized void write(byte b[], int off, int len) throws IOException {}         </p><p style="word-wrap: break-word; margin: 5px 0px;">public synchronized void flush() throws IOException {}       </p><p style="word-wrap: break-word; margin: 5px 0px;"> </p><p style="word-wrap: break-word; margin: 5px 0px;">    public void waitWhileFull(){    }            //当Chanel已经满了，写线程等待</p><p style="word-wrap: break-word; margin: 5px 0px;">public void waitWhileEmpty{    }        //当Chanel为空，读取线程等待</p><p style="word-wrap: break-word; margin: 5px 0px;">//以上是两个操作Chanel时的状态相关的方法。</p><p style="word-wrap: break-word; margin: 5px 0px;">//是一致性编程部分，典型的设计模式。</p><p style="word-wrap: break-word; margin: 5px 0px;">//这两个方法，包含在对应读或写方法的最前面。</p><p style="word-wrap: break-word; margin: 5px 0px;">}</p><p style="word-wrap: break-word; margin: 5px 0px;"> </p><p style="word-wrap: break-word; margin: 5px 0px;"> </p><p style="word-wrap: break-word; margin: 5px 0px;">       // PipedChanelInputStream.java</p><p style="word-wrap: break-word; margin: 5px 0px;">import java.io.*;</p><p style="word-wrap: break-word; margin: 5px 0px;"> </p><p style="word-wrap: break-word; margin: 5px 0px;">public class PipedChanelInputStream extends InputStream {</p><p style="word-wrap: break-word; margin: 5px 0px;">       private PipedChanel chanel ;</p><p style="word-wrap: break-word; margin: 5px 0px;">      </p><p style="word-wrap: break-word; margin: 5px 0px;">       public PipedChanelInputStream(PipedChanel chanel){</p><p style="word-wrap: break-word; margin: 5px 0px;">              this.chanel = chanel ;</p><p style="word-wrap: break-word; margin: 5px 0px;">       }</p><p style="word-wrap: break-word; margin: 5px 0px;">      </p><p style="word-wrap: break-word; margin: 5px 0px;">       public int read() throws IOException {</p><p style="word-wrap: break-word; margin: 5px 0px;">              return chanel.read();</p><p style="word-wrap: break-word; margin: 5px 0px;">       }   </p><p style="word-wrap: break-word; margin: 5px 0px;">   </p><p style="word-wrap: break-word; margin: 5px 0px;">    public  int read(byte b[], int off, int len)  throws IOException {</p><p style="word-wrap: break-word; margin: 5px 0px;">           return chanel.read(b,off,len);</p><p style="word-wrap: break-word; margin: 5px 0px;">    }</p><p style="word-wrap: break-word; margin: 5px 0px;">   </p><p style="word-wrap: break-word; margin: 5px 0px;">    public  int available() throws IOException {</p><p style="word-wrap: break-word; margin: 5px 0px;">           return chanel.available();</p><p style="word-wrap: break-word; margin: 5px 0px;">    }</p><p style="word-wrap: break-word; margin: 5px 0px;">   </p><p style="word-wrap: break-word; margin: 5px 0px;">    public  void close()  throws IOException {</p><p style="word-wrap: break-word; margin: 5px 0px;">           chanel.close();      </p><p style="word-wrap: break-word; margin: 5px 0px;">    }        </p><p style="word-wrap: break-word; margin: 5px 0px;">      </p><p style="word-wrap: break-word; margin: 5px 0px;">}</p><p style="word-wrap: break-word; margin: 5px 0px;"> </p><p style="word-wrap: break-word; margin: 5px 0px;"> </p><p style="word-wrap: break-word; margin: 5px 0px;">       // PipedChanelOutputStream.java</p><p style="word-wrap: break-word; margin: 5px 0px;">import java.io.*;</p><p style="word-wrap: break-word; margin: 5px 0px;"> </p><p style="word-wrap: break-word; margin: 5px 0px;">public class PipedChanelOutputStream extends OutputStream {</p><p style="word-wrap: break-word; margin: 5px 0px;">       private PipedChanel chanel ;</p><p style="word-wrap: break-word; margin: 5px 0px;">      </p><p style="word-wrap: break-word; margin: 5px 0px;">       public PipedChanelOutputStream(PipedChanel chanel){</p><p style="word-wrap: break-word; margin: 5px 0px;">              this.chanel = chanel ;</p><p style="word-wrap: break-word; margin: 5px 0px;">       }</p><p style="word-wrap: break-word; margin: 5px 0px;">   </p><p style="word-wrap: break-word; margin: 5px 0px;">    public synchronized void write(int b)  throws IOException {</p><p style="word-wrap: break-word; margin: 5px 0px;">           chanel.write(b);     </p><p style="word-wrap: break-word; margin: 5px 0px;">    }</p><p style="word-wrap: break-word; margin: 5px 0px;">    public synchronized void write(byte b[]) throws IOException {</p><p style="word-wrap: break-word; margin: 5px 0px;">           chanel.write(b);     </p><p style="word-wrap: break-word; margin: 5px 0px;">    }</p><p style="word-wrap: break-word; margin: 5px 0px;">    public synchronized void write(byte b[], int off, int len) throws IOException {</p><p style="word-wrap: break-word; margin: 5px 0px;">           chanel.write(b,off,len); </p><p style="word-wrap: break-word; margin: 5px 0px;">    }    </p><p style="word-wrap: break-word; margin: 5px 0px;">    public synchronized void flush() throws IOException {</p><p style="word-wrap: break-word; margin: 5px 0px;">           chanel.flush();</p><p style="word-wrap: break-word; margin: 5px 0px;">    }</p><p style="word-wrap: break-word; margin: 5px 0px;">    public synchronized void close()  throws IOException {</p><p style="word-wrap: break-word; margin: 5px 0px;">           chanel.close();      </p><p style="word-wrap: break-word; margin: 5px 0px;">    }   </p><p style="word-wrap: break-word; margin: 5px 0px;">}</p><p style="word-wrap: break-word; margin: 5px 0px;"> </p><p style="word-wrap: break-word; margin: 5px 0px;">       很简单的例子。我们可以体会适配器模式，可以体会软件设计的灵活性……</p><p style="word-wrap: break-word; margin: 5px 0px;">       上面的关于PipedInputStream和PipedOutputStream的例子，本质上是对一个Chanel的几个不同的适配。Chanel作为一种编程模式，在软件设计中有极其广泛的应用。下面一节是JMS的简洁阐述！</p><p style="word-wrap: break-word; margin: 5px 0px;">       以上的例子其实是一个典型的使用适配器</p></div><div style="word-wrap: break-word; margin: 5px 0px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(51, 51, 51); font-family: Arial; background-color: rgb(255, 255, 255); font-size: 14px;"><div> </div></div></div></div></div></div></div></div></div></div></div></div></span>
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