//WindowDestroyer.java

import java.awt.event.WindowAdapter; 
import java.awt.event.WindowEvent;

/**
If you register an object of this class as a listener with
any object of the class JFrame, then if the user clicks the 
close-window button in the JFrame, the object of this class
will end the program and close the JFrame.
*/
public class WindowDestroyer extends WindowAdapter
{
    public void windowClosing(WindowEvent e) 
    {
        System.exit(0);
    }
}