Java模拟弹球效果(监听键盘)

import java.awt.*;
import java.awt.event.*;

public class BallGame  extends Frame {
    
    Image sun = Toolkit.getDefaultToolkit().getImage("sun.jpg");
    
    double x=200;
    double y=200;
    boolean left,right,up,down;
    public void paint(Graphics  g){
        g.drawImage(sun, (int)x, (int)y, null);
        if(left){
            x = x-10;
        }
        if(right){
            x = x+10;
        }
        if(up){
            y = y-10;
        }
        if(down){
            y = y+10;
        }
        
    }
    
    void launchFrame(){
        setSize(500,400);
        setLocation(80, 80);
        setBackground(Color.black);
        setTitle("火星十一郎");
        myEvent();
        setVisible(true);
        new PaintThread().start();  
        addKeyListener(new KeyMonitor());
    }
    
    public static void main(String[] args){  
        new BallGame().launchFrame();
    }
    
    class PaintThread extends Thread {
        public void run(){
            while(true){
                repaint();
                try {
                    Thread.sleep(40);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }   //1秒=1000毫秒！
            }
        }
    }
    
    class  KeyMonitor extends KeyAdapter {
        public void keyPressed(KeyEvent e){
            if(37==e.getKeyCode()){
                left=true;
            }
            if(39==e.getKeyCode()){
                right = true;
            }
            if(38==e.getKeyCode()){
                up = true;
            }
            if(40==e.getKeyCode()){
                down = true;
            }
        }
        
        public void keyReleased(KeyEvent e){
            if(37==e.getKeyCode()){
                left=false;
            }
            if(39==e.getKeyCode()){
                right = false;
            }
            if(38==e.getKeyCode()){
                up = false;
            }
            if(40==e.getKeyCode()){
                down = false;
            }
        }
    }
    private void myEvent()
    {
        this.addWindowListener(new WindowAdapter()//窗口监听
        {
            public void windowClosing(WindowEvent e)
            {
                System.exit(0);
            }
        });
    }
}