菜鸟求教第2弹,请高手指教!

这段代码是按书上打的,但是我调试不出来,请大家帮我看看,是关于多线程的,顺便问问大家在工作中多线程用的多么,学什么实用点啊??
代码如下:(文件名我取的 ThreadTest.java)
 class CountingThread extends Thread
{
      public  void run()
        {
               System.out.println("Thread started:"+ this);
               for(int i=0; i<9; i++)
               System.out.print("i="+(i+1)+"\t");
               System.out.println("Thread stopped:"+ this);
        }
}
public class ThreadTest
{    
      public static void main(String args[])
       {   
       System.out.println("Statring ThreadTest");
       CountingThread thread1=new CountingThread();
       thread1.start();
       CountingThread thread2=new CountingThread();
       thread2.start();
       CountingThread thread3=new CountingThread();
       thread3.start();
       System.out.println("ThreadTest is done.");
       }
}
谢谢指教!!