public class CountDownLatchDemo {public static void main(String[] args) {final CountDownLatch latch = new CountDownLatch(2);System.out.println("等爸爸妈妈都来了就吃饭");new Thread(new Runnable() {@Overridepublic void run() {try {System.out.println("爸爸过来了");Thread.sleep(3000);latch.countDown();} catch (InterruptedException e) {e.printStackTrace();}}}).start();new Thread(new Runnable() {@Overridepublic void run() {try {System.out.println("妈妈过来了");Thread.sleep(3000);latch.countDown();} catch (InterruptedException e) {e.printStackTrace();}}}).start();try {latch.await();System.out.println("开饭了");} catch (InterruptedException e) {e.printStackTrace();}}
}

public class CyclicbarrierDemo {public static void main(String[] args) {int no = 3;final CyclicBarrier cyclicBarrier = new CyclicBarrier(no, new Runnable() {@Overridepublic void run() {System.out.println(Thread.currentThread().getName()+"发令员：3---2---1,跑！");}});for (int i = 0; i < no; i++) {new Thread(new Sportsman(cyclicBarrier)).start();}}static class Sportsman implements Runnable{CyclicBarrier cyclicBarrier;public Sportsman(CyclicBarrier cyclicBarrier) {this.cyclicBarrier = cyclicBarrier;}@Overridepublic void run() {try {Thread.sleep((int)(Math.random()*1000));System.out.println(Thread.currentThread().getName()+"准备好了，等待发令枪");cyclicBarrier.await();} catch (Exception e) {e.printStackTrace();}System.out.println(Thread.currentThread().getName()+"突突突");}}
}

public class SemaphoreDemo {public static void main(String[] args) {final Semaphore semaphore = new Semaphore(3);new Thread(new Runnable() {@Overridepublic void run() {try {semaphore.acquire(3);System.out.println(Thread.currentThread().getName()+"获取3个许可证");Thread.sleep(2000L);}catch (Exception e){e.printStackTrace();}finally {semaphore.release(3);}}}).start();new Thread(new Runnable() {@Overridepublic void run() {boolean flag = false;try {flag = semaphore.tryAcquire(1, 1, TimeUnit.SECONDS);if(flag){System.out.println(Thread.currentThread().getName()+"获取一个许可证");}else {System.out.println(Thread.currentThread().getName()+"获取失败！不能进入");}}catch (Exception e){e.printStackTrace();}finally {if(flag){//可以释放其他线程的信号量，如果没有获取到，不要释放，不然会有问题
                        semaphore.release();}}}}).start();}
}