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