java CyclicBarrier

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使用情况：你希望创建一组任务，他们并行执行，然后再进行下一个步骤之前等待，直到所有任务都完成

下面是一个赛马的例子，挺有意思的（java编程思想）

import java.util.concurrent.*;import java.util.*;public class Horse implements Runnable {private static int counter=0;private final int id=counter++;private int strides=0;private static Random rand=new Random(47);private static CyclicBarrier barrier;public Horse(CyclicBarrier barrier){this.barrier=barrier;}public synchronized int getStrides(){return strides;}@Overridepublic void run() {// TODO Auto-generated method stubtry{while(!Thread.interrupted()){synchronized(this){strides+=rand.nextInt(3);}barrier.await();}}catch(InterruptedException e){}catch(BrokenBarrierException e){throw new RuntimeException(e);}}public String toString(){return "Horse "+id+" ";}public String tracks(){StringBuilder s=new StringBuilder();for(int i=0;i<getStrides();i++){s.append("*");}s.append(id);return s.toString();}}

import java.util.concurrent.*;import java.util.*;public class HorseRace {public static final int FINISH_LINE=75;private List<Horse> horses =new ArrayList<Horse>();private ExecutorService exec=Executors.newCachedThreadPool();private CyclicBarrier barrier;public HorseRace(int nHorses,final int pause){barrier=new CyclicBarrier(nHorses,new Runnable(){public void run(){StringBuilder  s=new StringBuilder();for(int i=0;i<FINISH_LINE;i++)s.append("=");System.out.println(s);for(Horse horse:horses)System.out.println(horse.tracks());for(Horse horse:horses){if(horse.getStrides()>=FINISH_LINE){System.out.println(horse+" won!");exec.shutdownNow();return;}try{TimeUnit.MILLISECONDS.sleep(pause);}catch(InterruptedException e){System.out.println("barrier-action sleep interrupted");}}}});for(int i=0;i<nHorses;i++){Horse horse=new Horse(barrier);horses.add(horse);exec.execute(horse);}}/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubint nHorses=7;int pause=200;new HorseRace(nHorses,pause);}}

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