Use final keyword when possible

[yungpanda]

It's a good practice to use the final keyword as much as possible.
Every variable that isn't going to change it's value should be declared final.

Global variables
If you have constant fields they should be declared final for performance. The order of static and final doesn't matter, but try to keep the order the same in all your files.
E.g. LoginActivity has private static final and private final static which looks messy.

Variables inside methods
See http://programmers.stackexchange.com/questions/115690/why-declare-final-variables-inside-methods
*.... It's a good habit to get into along with a number of others; eg: "Make everything final by default, unless otherwise required", "Make everything private by default, unless otherwise required".... *

[mbamelis]

Classes have been skimmed to a certain extent to apply these principals.

In addition, comment markup has been added to each class. Big sections are labeled with 3-line comment blocks. Titles include (all in caps in the java files): Nested Classes, Nested Interfaces, Static Members, Static Methods, Constructors, Members and, Methods
Each section is further divided with single code lines. These divide each section in a public, protected and, private subsection.