How to Define function in java

<%--
Copyright (c) 2002 by Phil Hanna
All rights reserved.

You may study, use, modify, and distribute this
software for any purpose provided that this
copyright notice appears in all copies.

This software is provided without warranty
either expressed or implied.
--%>
<%!
public int sum(int a, int b)
{
return a + b;
}
%>
2 + 2 = <%= sum(2, 2) %>