java窗口无法关闭_用java生成的窗口不能关闭

代码如下：packagelesson8;importjava.awt.*;importjava.awt.event.*;publicclassMyFrame{publicstaticvoidmain(String[]args){Framef=newFrame();Buttonbtn1=newButton("HelloWorld"...

代码如下：

package lesson8;

import java.awt.*;

import java.awt.event.*;

public class MyFrame {

public static void main(String[] args) {

Frame f=new Frame();

Button btn1=new Button("HelloWorld");

Button btn2=new Button("North");

Button btn3=new Button("South");

Button btn4=new Button("Center");

Button btn5=new Button("West");

//f.setLayout(new BorderLayout(10,10));

//f.setLayout(new FlowLayout(FlowLayout.LEFT));

//f.setLayout(new GridLayout(2,3,10,20));

//f.setLayout(new CardLayout());

f.add(btn1,"North");

f.add(btn2,"West");

f.add(btn3,"South");

f.add(btn4,"East");

f.add(btn5,"Center");

f.setSize(400,600);

f.setLocation(100,100);

f.setBackground(Color.BLUE);

f.addWindowListener(new MyWindowListener());

f.show();

}

}

class MyWindowListener implements WindowListener

{

public void windowOpened(WindowEvent e){

}

public void windowClosing(WindowEvent e)

{

}

public void windowClosed(WindowEvent e)

{

System.exit(0);

}

public void windowIconified(WindowEvent e){

}

public void windowDeiconified(WindowEvent e){

}

public void windowActivated(WindowEvent e)

{

}

public void windowDeactivated(WindowEvent e){

}

}

请问为什么不能关闭？

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