线程交替问题
想定义两个线程交替运行，以sum为指标，sum=0 运行线程0，在线程0里把，sum设为1；sum=1时运行线程1，在线程1里，把sum置为0，依次循环，并计算线程交替时间。
结果应该是
0
1
0
1
0
1
0
1
。。。。

高手看看我的程序哪里出错：

class Number0 extends Thread{
   
  //public long lasting;
  public void run()
  {
  if (SumStore.sum == 0)
  {
  SumStore.sum = 1;
  System.out.println("thread0 and sum is " + SumStore.sum);
   
  }
  //lasting = System.currentTimeMillis();
  //long cost =
  //System.out.println("threadswitch time " + cost);
  //return;
  //}
  }
   
   
}


class Number1 extends Thread{
   
  public long starting,lasting;
  public void run()
  {
   
  if (SumStore.sum == 1)
  {
  SumStore.sum = 0;  
  System.out.println("thread1 and sum is " + SumStore.sum);
  }
   
   
   
  //starting = System.currentTimeMillis();
  //long cost = starting - lasting;
  //System.out.println("threadswitch time " + cost);
  }
}

class SumStore {

  public static int sum = 0;

}
/////////////////////////////////////////////////////////////////////////
public class threadswitching
{

/**
  * @param args
  */
public static void main(String[] args) throws Exception
{
   
  for(int i=1; i<3; i++){
Thread t1 = new Number0();
Thread t2 = new Number1();
t1.start();
t2.start();
  }

}
}
 

------解决方案--------------------

Java code

 
 class Number0 extends Thread { 
 	// public long lasting; 
 	public void run() { 
 		while (true) { 
 			synchronized (SumStore.class) { 
 				try { 
 					if (SumStore.sum == 0) { 
 						SumStore.sum = 1; 
 						System.out.println("thread0 and sum is  " 
 								+ SumStore.sum); 
 					} 
 					SumStore.class.notifyAll(); 
 					Thread.sleep(300); 
 				} catch (Exception e) { 
 					// TODO Auto-generated catch block 
 					e.printStackTrace(); 
 				} 
 			} 
 		} 
 		// lasting = System.currentTimeMillis(); 
 		// long cost = 
 		// System.out.println("threadswitch time " + cost); 
 		// return; 
 		// } 
 	} 
  
 } 
  
 class Number1 extends Thread { 
 	public long starting, lasting; 
 	public void run() { 
 		while (true) { 
 			synchronized (SumStore.class) { 
 				try { 
 					SumStore.class.wait(); 
 					if (SumStore.sum == 1) { 
 						SumStore.sum = 0; 
 						System.out.println("thread1 and sum is  " 
 								+ SumStore.sum); 
 					} 
 					Thread.sleep(300); 
 				} catch (InterruptedException e) { 
 					// TODO Auto-generated catch block 
 					e.printStackTrace(); 
 				} 
 			} 
 		} 
 		// starting = System.currentTimeMillis(); 
 		// long cost = starting - lasting; 
 		// System.out.println("threadswitch time " + cost); 
 	} 
 } 
  
 class SumStore {