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();
}

}
}


[解决办法]

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 {  
 
 public static int sum = 0; 
 } 
  
 // /////////////////////////////////////////////////////////////////////// 
 public class threadswitching { 
 /** 
  * @param args 
  */ 
 public static void main(String[] args) throws Exception { 
 Thread t1 = new Number0(); 
 Thread t2 = new Number1(); 
 t1.start(); 
 t2.start(); 
  
 } 
 }

[解决办法]
不知道你说的问题是不是:为什么程序的结果是
1
0
1
0
而不是
0
1
0
1
0
1
0
1
修改如下:
class Number0 extends Thread{

//public long lasting;
public void run()
{
if (SumStore.sum == 0)
{
System.out.println("thread0 and sum is " + SumStore.sum);
//上面的输出放在SumStore.sum = 1; 之前
SumStore.sum = 1;

}
//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)
{
System.out.println("thread1 and sum is " + SumStore.sum); //把这句放在SumStore.sum = 0;
SumStore.sum = 0;
}



//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();
}

}
}