Window events-handling by WindowListener

import java.applet.Applet;
import java.awt.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;

public class WindowEventExample extends Applet
		             implements WindowListener,
				        ActionListener {
    String lineSep;
    TextArea textAreaObj;
    Frame frameObj;
    Button btnOne, btnTwo;
    static final String SHOW = "show";
    static final String CLEAR = "clear";
    

    public void init() {
	btnOne = new Button("Click to bring up a window.");
	btnOne.setActionCommand(SHOW);
	btnOne.addActionListener(this);

	btnTwo = new Button("Click to clear the display.");
	btnTwo.setActionCommand(CLEAR);
	btnTwo.addActionListener(this);

	textAreaObj = new TextArea(5, 20);
	textAreaObj.setEditable(false);

	setLayout(new BorderLayout());
	add("North", btnOne);
	add("Center", textAreaObj);
	add("South", btnTwo);

 
	frameObj = new Frame("Frame with Window Event ");
	frameObj.addWindowListener(this);
	frameObj.add("Center",
		   new Label("The applet listens to this window for window events."));
	frameObj.pack();

	lineSep = System.getProperty("line.separator");
    }

    public void stop() {
	frameObj.setVisible(false);
    }

    public void windowClosing(WindowEvent e) {
    	frameObj.setVisible(false);
	printMessage("Window closing", e);
    }

    public void windowClosed(WindowEvent e) {
	printMessage("Window closed", e);
    }

    public void windowOpened(WindowEvent e) {
	printMessage("Window opened", e);
    }

    public void windowIconified(WindowEvent e) {
	printMessage("Window iconified", e);
    }

    public void windowDeiconified(WindowEvent e) {
	printMessage("Window deiconified", e);
    }

    public void windowActivated(WindowEvent e) {
	printMessage("Window activated", e);
    }

    public void windowDeactivated(WindowEvent e) {
	printMessage("Window deactivated", e);
    }

    void printMessage(String prefix, WindowEvent e) {
	textAreaObj.append(prefix
		       + ": "
		       + e.getWindow()
		       + lineSep); 
    }

    public void actionPerformed(ActionEvent e) {
	if (e.getActionCommand() == SHOW) {
	    frameObj.pack();
	    frameObj.setVisible(true);
	} else {
	    textAreaObj.setText("");
	}
    }
}