  import java.awt.event.ActionListener; 
  import javax.swing.JButton; 
  import javax.swing.JFrame; 
 
  /** 
     This program demonstrates how to install an action listener. 
  */ 
  public class ButtonViewer 
  { 
    public static void main(String[] args) 
    { 
       JFrame frame = new JFrame(); 
       JButton button = new JButton(Click me!); 
      frame.add(button); 
 
       ActionListener listener = new ClickListener(); 
       button.addActionListener(listener); 
 
      frame.setSize(FRAME_WIDTH, FRAME_HEIGHT); 
       frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
       frame.setVisible(true); 
    } 
 
   private static final int FRAME_WIDTH = 100; 
    private static final int FRAME_HEIGHT = 60; 
 }
