non-static nested class vs. static nested class

http://stackoverflow.com/questions/1353309/java-static-vs-non-static-inner-class

A non-static nested class has full access to the members of the class within which it is nested. A static nested class does not have a reference to a nesting instance, so a static nested class cannot invoke non-static methods or access non-static fields of an instance of the class within which it is nested.