import java.awt.event.*;
import javax.swing.*;

public class P0705 
{
    public static void main (String[] args)
    {
        CloseFrame frame=new CloseFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.addWindowListener(new WindowAdapter()
        {
            public void windowClosing(WindowEvent e)
            {
                JOptionPane.showMessageDialog(null,output,"close",JOptionPane.CLOSED_OPTION);
                System.exit(0);
            }
        });
        frame.show();    
    }
}

class CloseFrame extends JFrame implements  ActionListener
{
    public CloseFrame()
    {
        setTitle("弹出窗口");
        setSize(300,300);
    }
}

题目要求关闭窗口弹出对话框，提示是否确定关闭。
我写的程序有错误，能帮我改改吗？？