CyclicBarrier ------仿真赛马游戏

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

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 b) {
       this.barrier = b;
   }

   public synchronized int getStrides() {
       return strides;
   }

   @Override
   public void run() {
       try {
           while(!Thread.interrupted()){
               synchronized (this) {
                   strides += rand.nextInt(3);
               }
               barrier.await();//循环等待
           }
       } catch (InterruptedException e) {
           // TODO: handle InterruptedException
       } catch (BrokenBarrierException e) {
           throw new RuntimeException(e);
       }
   }

   @Override
   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();
   }
}

public class HorseRace {
   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() {
           @Override
           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 {
                   //可以睡眠，显示出效果，否则复很快执行完，看不出明显的效果
                   TimeUnit.MILLISECONDS.sleep(pause);
               } catch (InterruptedException e) {
                   System.out.println("屏障—行为 sleep interrupted");
               }
           }
       });
       for (int i = 0; i < nHorses; i++) {
           Horse horse = new Horse(barrier);
           horses.add(horse);
           exec.execute(horse);
       }
   }

   public static void main(String[] args) {
       int nHorses = 7;
       int pause = 200;
       if(args.length > 0){
           int n = new Integer(args[0]);
           nHorses = n > 0 ? n : nHorses;
       }
       if(args.length > 1){
           int p = new Integer(args[1]);
           pause = p > 1 ? p : pause;
       }

       new HorseRace(nHorses, pause);
   }
}

效果图：

巴特西

CyclicBarrier ------仿真赛马游戏

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