WindowEvent.WINDOW_CLOSED has the following syntax.
public static final int WINDOW_CLOSED
In the following code shows how to use WindowEvent.WINDOW_CLOSED field.
/* w w w . jav a 2s . c o m*/ import java.awt.event.WindowEvent; import javax.swing.JFrame; public class Main extends JFrame { public Main() { setDefaultCloseOperation(EXIT_ON_CLOSE); enableEvents(java.awt.AWTEvent.WINDOW_EVENT_MASK); } protected void processWindowEvent(WindowEvent e) { if (e.getID() == WindowEvent.WINDOW_CLOSED) { System.out.println(WindowEvent.WINDOW_CLOSED); dispose(); System.exit(0); } super.processWindowEvent(e); // Pass on the event } public static void main(String[] a) { Main window = new Main(); window.setBounds(30, 30, 300, 300); window.setVisible(true); } }