CyclicBarrie

个人学习笔记，如有错误欢迎指正。。

 

 

CyclicBarrier 类用于阻塞一个或多个线程，等待其它线程完成任务，直至所有线程都完成各自的任务，才会解除阻塞继续执行。 

 

 构建器 CyclicBarrier   （int n,Runnable runnable）

 

await()方法被调用时，计数器N减一，如果计数据N>0，则当前线程阻塞，如果计数器N==0时，则 Runnable 被调用， Runnable 执行完成后，所有因为await()方法阻塞的线程被唤醒。N被再次重置为初始值，这个  CyclicBarrier  可以被再次复用。 

 

示例：计算1+2+3+4+5+6+........+10000=??

    由多个线程执行计算，每个线程计算的结果相加就等于最终结果，并每个线程打印出最终结果。

 

public class TestCyclicBarrier implements Runnable{
	CyclicBarrier cyclicBarrier = null;
	int startValue;
	int endValue;
	AtomicLong total ;
	String threadName ; 
	String resultReceiver;
	public TestCyclicBarrier(String threadName,CyclicBarrier cyclicBarrier,AtomicLong total,int startValue,int endValue,String resultReceiver){
		this.cyclicBarrier =  cyclicBarrier;
		this.startValue = startValue;
		this.endValue = endValue;
		this.total = total;
		this.threadName = threadName;
		this.resultReceiver = resultReceiver;
	}
	static SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
	@Override
	public void run() {
		// TODO Auto-generated method stub
		try{
			
			//开始计算
			System.out.println(sdf.format(new Date())+": "+this.threadName+"  count  start:"+startValue+"+"+(startValue+1)+"+"+(startValue+2)+" .....+"+endValue+"=?");
			Thread.sleep(2000);
			
			long total = 0;
			for(int i=startValue;i<endValue;i++){
				total+= i;
			}
			System.out.println(sdf.format(new Date())+": "+this.threadName+"  count finish:"+startValue+"+"+(startValue+1)+"+"+(startValue+2)+" .....+"+endValue+" = "+total);
			this.total.addAndGet(total);//计算完成
			cyclicBarrier.await();//本线程计算工作完成，阻塞等待其它线程完成完成计算
			System.out.println(sdf.format(new Date())+": "+this.threadName+" send result to "+resultReceiver+":"+this.total.get());//所有任务计算完成，将最终结果发送给某人
			System.out.println(sdf.format(new Date())+": "+this.threadName+" to exit");//线程退出
		}catch(Exception e){
			e.printStackTrace();
		}
	}
	public static void main(String args []){
		final AtomicLong total = new AtomicLong();
		int startValue = 1;
		int endValue = 10000;
		int difference = endValue-startValue;
		int threadNum = difference/1000;//每条线程计算1000个数据相加
		if(difference%100>0){//计算需要线程数
			threadNum++;
		}
		CyclicBarrier cyclicBarrier = new CyclicBarrier(threadNum,new Runnable(){
			
			@Override
			public void run() {//把有线程任务执行完成时，调用。
				// TODO Auto-generated method stub
				System.out.println(sdf.format(new Date())+": ALL thread count finish , count result ="+total.get());
			}
			
			
		});
		 ExecutorService executorService=Executors.newCachedThreadPool();
		for(int i=0;i<threadNum;i++){//任务拆分，发给多个线程执行
			int startValueForThread = startValue+(i*1000);
			int endValueForThread = startValue+(i*1000)+1000;
			if(endValueForThread>endValue){
				endValueForThread= endValue;
			}
			TestCyclicBarrier testCyclicBarrier = new TestCyclicBarrier("thread_"+i,cyclicBarrier,total,startValueForThread,endValueForThread,"person"+i);
			executorService.execute(testCyclicBarrier);//开始执行任务线程
			
		}
		
	}
}

 程序输出：

2013-12-01 22:46:02: thread_1  count  start:1001+1002+1003 .....+2001=?

2013-12-01 22:46:02: thread_0  count  start:1+2+3 .....+1001=?

2013-12-01 22:46:02: thread_2  count  start:2001+2002+2003 .....+3001=?

2013-12-01 22:46:02: thread_3  count  start:3001+3002+3003 .....+4001=?

2013-12-01 22:46:02: thread_4  count  start:4001+4002+4003 .....+5001=?

2013-12-01 22:46:02: thread_6  count  start:6001+6002+6003 .....+7001=?

2013-12-01 22:46:02: thread_5  count  start:5001+5002+5003 .....+6001=?

2013-12-01 22:46:02: thread_7  count  start:7001+7002+7003 .....+8001=?

2013-12-01 22:46:02: thread_9  count  start:9001+9002+9003 .....+10000=?

2013-12-01 22:46:02: thread_8  count  start:8001+8002+8003 .....+9001=?

2013-12-01 22:46:04: thread_1  count finish:1001+1002+1003 .....+2001 = 1500500

2013-12-01 22:46:04: thread_0  count finish:1+2+3 .....+1001 = 500500

2013-12-01 22:46:04: thread_2  count finish:2001+2002+2003 .....+3001 = 2500500

2013-12-01 22:46:04: thread_3  count finish:3001+3002+3003 .....+4001 = 3500500

2013-12-01 22:46:04: thread_4  count finish:4001+4002+4003 .....+5001 = 4500500

2013-12-01 22:46:04: thread_5  count finish:5001+5002+5003 .....+6001 = 5500500

2013-12-01 22:46:04: thread_6  count finish:6001+6002+6003 .....+7001 = 6500500

2013-12-01 22:46:04: thread_7  count finish:7001+7002+7003 .....+8001 = 7500500

2013-12-01 22:46:04: thread_9  count finish:9001+9002+9003 .....+10000 = 9490500

2013-12-01 22:46:04: thread_8  count finish:8001+8002+8003 .....+9001 = 8500500

2013-12-01 22:46:04: ALL thread count finish , count result =49995000

2013-12-01 22:46:04: thread_8 send result to person8:49995000

2013-12-01 22:46:04: thread_8 to exit

2013-12-01 22:46:04: thread_1 send result to person1:49995000

2013-12-01 22:46:04: thread_1 to exit

2013-12-01 22:46:04: thread_2 send result to person2:49995000

2013-12-01 22:46:04: thread_2 to exit

2013-12-01 22:46:04: thread_3 send result to person3:49995000

2013-12-01 22:46:04: thread_3 to exit

2013-12-01 22:46:04: thread_5 send result to person5:49995000

2013-12-01 22:46:04: thread_6 send result to person6:49995000

2013-12-01 22:46:04: thread_9 send result to person9:49995000

2013-12-01 22:46:04: thread_0 send result to person0:49995000

2013-12-01 22:46:04: thread_9 to exit

2013-12-01 22:46:04: thread_6 to exit

2013-12-01 22:46:04: thread_5 to exit

2013-12-01 22:46:04: thread_4 send result to person4:49995000

2013-12-01 22:46:04: thread_4 to exit

2013-12-01 22:46:04: thread_7 send result to person7:49995000

2013-12-01 22:46:04: thread_0 to exit

2013-12-01 22:46:04: thread_7 to exit