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That is not java. It looks like javascript which is a different language.

There are no Functions in java. Are you asking about methods?
See the tutorial: Defining Methods (The Java™ Tutorials > Learning the Java Language > Classes and Objects)

Do you have some code you are having problems with? Post the code that shows the problems you are having.

Take a look at the tutorial: http://docs.oracle.com/javase/tutorial/reallybigindex.html