fourthwindow.java

《A first book of java》by Gary J.Bronson 北大出版社

import javax.swing.*;
import java.awt.event.*;
public class FourthWindow extends JFrame
{
  private JFrame mainFrame;

  public FourthWindow() // a constructor
  {
    mainFrame = new JFrame("Fourth GUI Window");

   
    mainFrame.setSize(300,150);
    mainFrame.show();

     // create and register the handler in one statement
    mainFrame.addWindowListener(new WinHandler()); 
  } 

  public static void main(String args[])
  {
    new FourthWindow(); 
  }
}  // end of GUI class

  // extend an adapter class to handle window events
class WinHandler extends WindowAdapter
{
  public void windowClosing(WindowEvent e) {System.exit(0);}
}  // end of listener class