ActionListener

A button listener must implement the ActionListener interface. ActionListener is an interface (not a class) that contains a single method:

public void actionPerformed( ActionEvent evt) ;

The ActionEvent parameter is an Event object that represents an event (a button click). It contains information that can be used in responding to the event. ActionListener is an interface. A class that implements the interface must contain an actionPerformed() method.

Import the package java.awt.event.* if you are dealing with events.

import java.awt.*; 
import java.awt.event.*;
import java.awt.*; 

class ButtonFrame extends JFrame implements ActionListener
{
  JButton bChange;

  ButtonFrame()     
  {
     . . . . . .
  }

  
  // listener method for the ActionListener interface
  public void actionPerformed( ActionEvent evt)
  {
     . . . . . .
  }

}

The listener object could be defined in a class separate from the frame class. In our example, the same class that holds the component is also the listener for its events.