在eclipse环境下JAVA窗口问题？

package Stringtest;

import java.awt.Frame;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
//输出一个窗口，然后按上下左右键使之按键移动。
public class Test{  
    public static void main(String[] args){  
        //窗口名
        new MyFrame("按键位移测试");  
    }     
}  
  
class MyFrame extends Frame{
    /**
     *
     */
    private static final long serialVersionUID = 1L;
    int x=300;  
    int y=300;  
    int w=400;  
    int h=300;  
    private int num=0;  
    MyFrame(String s){
        super(s);
        setBounds(x,y,w,h);  
        setResizable(false);  
        addKeyListener(new KeyAdapter(){  
            public void keyPressed(KeyEvent e){  
                    switch(e.getKeyCode()){  
                        case KeyEvent.VK_UP:  
                            y-=50;  
                            break;  
                        case KeyEvent.VK_DOWN:  
                            y+=50;  
                            break;  
                        case KeyEvent.VK_LEFT:  
                            x-=50;  
                            break;  
                        case KeyEvent.VK_RIGHT:  
                            x+=50;  
                            break;        
                    }  
                    setBounds(x,y,w,h);  
            }  
        });  
        setVisible(true);  
        this.addWindowListener(new WindowAdapter(){  
            public void windowClosing(WindowEvent e){  
                setVisible(false);  
                System.exit(0);   
            }  
        });  
    }  
}