Using Object-Oriented Patterns - Beginning Java Programming: The Object-Oriented Approach - page 596

frame.setSize(400, 400);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Create our listener
MouseListener listener = new MouseListener(){
public void mouseClicked(MouseEvent e) {
JOptionPane.showMessageDialog(null, "You clicked the mouse!");
}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
public void mousePressed(MouseEvent e) {}
public void mouseReleased(MouseEvent e) {}
};
// Register
frame.addMouseListener(listener);
// Go
frame.setVisible(true);
}
}
In some other cases, you'll see the subject acting as its own listener ( GUIListenerExample extends
JFrame implements MouseListener ):
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
public class GUIListenerExample extends JFrame implements MouseListener {
public GUIListenerExample() {
this.addMouseListener(this);
}
public void mouseClicked(MouseEvent e) {
JOptionPane.showMessageDialog(null, "You clicked the mouse!");
}
public void mouseEntered(MouseEvent e) {}
public void mouseExited(MouseEvent e) {}
public void mousePressed(MouseEvent e) {}
public void mouseReleased(MouseEvent e) {}
public static void main(String[] args) {
// Create our subject
JFrame frame = new GUIListenerExample();
frame.setSize(400, 400);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// Go
frame.setVisible(true);
}
}