Credits to Dmitry Beransky on the advanced-java@discuss.develop.com list.

import java.util.Date; import java.io.IOException; public class When { public static void main(String args[]) throws IOException {

Date d = new Date( When.class.getResource("When.class") .openConnection() .getLastModified() );

System.out.println("This class was compiled on " + d); } }

Just check the .class file modification time. Clever!