/*** 简单模拟一下对战平台中玩家需要完全准备好了,才能进入游戏的场景。* * @author BFD_526* */
public class CyclicBarrierTest {public static void main(String[] args) {test();}// 同步屏障static void test() {ExecutorService service = Executors.newFixedThreadPool(5);CyclicBarrier barrier = new CyclicBarrier(5);for (int i = 0; i < 5; i++) {service.execute(new Player("玩家" + i, barrier));}service.shutdown();}// 同步屏障重置static void test1() {ExecutorService service = Executors.newFixedThreadPool(5);CyclicBarrier barrier = new CyclicBarrier(5);for (int i = 0; i < 5; i++) {service.execute(new Player("玩家" + i, barrier));}for (int i = 5; i < 10; i++) {service.execute(new Player("玩家" + i, barrier));}service.shutdown();}// 在同步屏障结束后，启动优先线程static void test2() {ExecutorService service = Executors.newFixedThreadPool(5);CyclicBarrier ba = new CyclicBarrier(5, new Runnable() {@Overridepublic void run() {System.out.println("所有玩家已就位");}});for (int i = 0; i < 5; i++) {service.execute(new Player("玩家" + i, ba));}}
}class Player implements Runnable {private final String name;private final CyclicBarrier barrier;public Player(String name, CyclicBarrier barrier) {this.name = name;this.barrier = barrier;}public void run() {try {TimeUnit.SECONDS.sleep(1 + (new Random().nextInt(3)));System.out.println(name + "已准备,等待其他玩家准备...");barrier.await();TimeUnit.SECONDS.sleep(1 + (new Random().nextInt(3)));System.out.println(name + "已加入游戏");} catch (InterruptedException e) {System.out.println(name + "离开游戏");} catch (BrokenBarrierException e) {System.out.println(name + "离开游戏");}}
}

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public int await() throws InterruptedException, BrokenBarrierException {try {return dowait(false, 0L);} catch (TimeoutException toe) {throw new Error(toe); // cannot happen;
    }
}

private int dowait(boolean timed, long nanos)throws InterruptedException, BrokenBarrierException,TimeoutException {final ReentrantLock lock = this.lock;// 获取“独占锁(lock)”
    lock.lock();try {// 保存“当前的generation”final Generation g = generation;// 若“当前generation已损坏”，则抛出异常。if (g.broken)throw new BrokenBarrierException();// 如果当前线程被中断，则通过breakBarrier()终止CyclicBarrier，唤醒CyclicBarrier中所有等待线程。if (Thread.interrupted()) {breakBarrier();throw new InterruptedException();}// 将“count计数器”-1int index = --count;// 如果index=0，则意味着“有parties个线程到达barrier”if (index == 0) {  // trippedboolean ranAction = false;try {// 如果barrierCommand不为null，则执行该动作final Runnable command = barrierCommand;if (command != null)command.run();ranAction = true;// 唤醒所有等待线程，并更新generation
               nextGeneration();return 0;} finally {if (!ranAction)breakBarrier();}}// 当前线程一直阻塞，直到“有parties个线程到达barrier” 或 “当前线程被中断” 或 “超时”这3者之一发生，// 当前线程才继续执行。for (;;) {try {// 如果不是“超时等待”，则调用awati()进行等待；否则，调用awaitNanos()进行等待if (!timed)trip.await();else if (nanos > 0L)nanos = trip.awaitNanos(nanos);} catch (InterruptedException ie) {// 如果等待过程中，线程被中断，则执行下面的函数if (g == generation && ! g.broken) {breakBarrier();throw ie;} else {Thread.currentThread().interrupt();}}// 如果“当前generation已经损坏”，则抛出异常if (g.broken)throw new BrokenBarrierException();// 如果“generation已经换代”，则返回indexif (g != generation)return index;// 如果是“超时等待”，并且时间已到，则通过breakBarrier()终止CyclicBarrier，唤醒CyclicBarrier中所有等待线程if (timed && nanos <= 0L) {breakBarrier();throw new TimeoutException();}}} finally {// 释放“独占锁(lock)”
        lock.unlock();}
}

private Generation generation = new Generation();private static class Generation {boolean broken = false;
}

//换代private void nextGeneration() {trip.signalAll();count = parties;generation = new Generation();
}

private void breakBarrier() {generation.broken = true;count = parties;trip.signalAll();
}