点关闭按钮让面板封闭

import java.awt.event.*;import java.awt.*;class TestStopWatch extends Frame{    public TestStopWatch()    {        addWindowListener(new WindowAdapter()        {            public void WindowClosing(WindowEvent e)            {                dispose();                System.exit(0);            }        });    }    public static void main(String []args)    {        TestStopWatch sw=new TestStopWatch();        sw.setSize(400,400);        sw.setVisible(true);    }}