一个JAVA小程序的问题

//

import java.awt.*;
import java.awt.event.*;
public class TestMyButton extends Frame
{
public TestMyButton()
{
addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
dispose();
System.exit(0);
}
});
}

public static void main(String[] args) {

// TODO, add your application code
System.out.println("Starting TestMyButton...");
TestMyButton mainFrame = new TestMyButton();

MyButton btn1 = new MyButton("你来抓我啊!");
MyButton btn2 = new MyButton("你来抓我啊!");
btn1.setFriend(btn2);
btn2.setFriend(btn1);

mainFrame.add(btn1,"North");
mainFrame.add(btn2,"South");

mainFrame.setSize(400,400);
mainFrame.setTitle("TestMybutton");
mainFrame.setVisible(true);
btn2.setVisible(false);
}
}

//

import java.awt.*;
import java.awt.event.*;
public class MyButton extends Button
{
private MyButton friend = null;
public MyButton(String title)
{

super(title);
enableEvents(AWTEvent.MOUSE_EVENT_MASK);
}

public void setFriend(MyButton friend)
{
this.friend = friend;
}
public void processMouseMotionEvent(MouseEvent e)
{
setVisible(false);
friend.setVisible(true);
}
}

/