An instance variable differs from a local variable in the nature of its scope and its lifetime. The entire class makes up the scope of an instance variable, not the method in which it was declared.

Abstract classes and interfaces in Java serve fundamentally different purposes. Learn the differences between these Java language elements and how to use them in your programs.

There are other ways you can categorize variables in Java, and other ways you can manipulate data. For instance, a constant is a variable whose value never changes.