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class ButtonFrame extends JFrame implements ActionListener
{
  JButton bChange ;

  // constructor   
  public ButtonFrame() 
  {
    bChange = new JButton("Click Me!"); 
    getContentPane().setLayout( new FlowLayout() );  
    getContentPane().add( bChange ); 
    setDefaultCloseOperation( WindowConstants.EXIT_ON_CLOSE );    
  }
   
  // listener method required by the interface
  public void actionPerformed( ActionEvent evt)
  {
     . . . . . .
  }
}

In this style of GUI programming, one object (the ButtonFrame object) is playing two roles: it is the container object that holds a GUI component, and it is also the listener object for that component.

Implementing ActionListener is not enough. The listener must still be registered with the JButton.