from StackOverflow

Author: dave-ck

src/FixedSizePriorityQueue.java

@@ -0,0 +1,47 @@
+import java.util.Comparator;
+import java.util.TreeSet;
+
+// taken from https://stackoverflow.com/questions/7878026/is-there-a-priorityqueue-implementation-with-fixed-capacity-and-custom-comparato
+
+public class FixedSizePriorityQueue<E> extends TreeSet<E> {
+	
+	private int elementsLeft;
+	
+	public FixedSizePriorityQueue(int maxSize, Comparator<E> comparator) {
+		super(comparator);
+		this.elementsLeft = maxSize;
+	}
+	
+	
+	/**
+	 * @return true if element was added, false otherwise
+	 * */
+	@Override
+	public boolean add(E e) {
+		if (elementsLeft == 0 && size() == 0) {
+			// max size was initiated to zero => just return false
+			return false;
+		} else if (elementsLeft > 0) {
+			// queue isn't full => add element and decrement elementsLeft
+			boolean added = super.add(e);
+			if (added) {
+				elementsLeft--;
+			}
+			//System.out.println("Element added: " + e);
+			//System.out.println("Variable added has value: " + added);
+			return added;
+		} else {
+			// there is already 1 or more elements => compare to the least
+			int compared = super.comparator().compare(e, this.first());
+			if (compared == 1) {
+				// new element is larger than the least in queue => pull the least and add new one to queue
+				pollFirst();
+				super.add(e);
+				return true;
+			} else {
+				// new element is less than the least in queue => return false
+				return false;
+			}
+		}
+	}
+}