Still struggling with Java?
Me too (who isn't?).
In this particular case, it's about static methods, accessing class variables.
A lesson learned: do not add state to classes with static methods.
Concurrency will lead to problems!

See for instance http://www.javaworld.com/javaworld/javaqa/2001-11/03-qa-1121-mrhappy.html
When you declare a method as static, you define that method as being a class method. A class method applies to the class as opposed to any particular instance. The behavior instigated by a class method does not rely on the state of a particular instance. In fact, a static method cannot rely on an instance's state since static methods lack access to this reference. Instead, the behavior of a class method either depends on a state that all objects share at the class level, or is independent of any state at all.

Nice name in the URL: mrhappy!

Actually it's Mr. Happy Object, see
http://www.javaworld.com/javaqa/2002-03/01-qa-0315-happyevent.html?page=1
Woe to he who angers MrHappyObject!