小编use*_*432的帖子

public class Basics extends Applet{

int x = 0;

int y = 0;

    public void init(){
        setSize(500,500);
    }

    public void start(){
        Thread a = new Thread();
        a.start();
    }

    public void run(){
        while(true){
            x = 100;
            y = 100;                
            repaint();
            try{
                Thread.sleep(18);
            }
            catch(InterruptedException e){}
        }

    public void paint(Graphics g){
        g.setColor(Color.red);
        g.fillRect(this.x,this.y,25,25);
    }

}

不应该递增x和y然后重新绘制允许方块移动