import java.awt.*;import java.awt.event.*;import java.applet.*;public class Example19_7 extends Applet implements Runnable{Thread 紅色球,蘭色球; Graphics redPen,bluePen;int t=0;  public void init()  { 紅色球=new Thread(this); 蘭色球=new Thread(this);   redPen=getGraphics();  bluePen=getGraphics();   redPen.setColor(Color.red);  bluePen.setColor(Color.blue);  }  public void start()  {紅色球.start();蘭色球.start();  }  public void run()  { while(true)   { t=t+1;   if(Thread.currentThread()==紅色球)    {if(t>100) t=0;      redPen.clearRect(0,0,110,400);      redPen.fillOval(50,(int)(1.0/2*t*9.8),5,5);      try{紅色球.sleep(40);}        catch(InterruptedException e){}     }     else if(Thread.currentThread()==蘭色球)      {bluePen.clearRect(120,0,900,500);        bluePen.fillOval(120+7*t,(int)(1.0/2*t*9.8),5,5);        try{蘭色球.sleep(40);}        catch(InterruptedException e){}      }     }     } }