//演示 CountDownLatch
public class CountDownLatchDemo {
    //6個(gè)同學(xué)陸續(xù)離開教室之后，班長(zhǎng)鎖門
    public static void main(String[] args) throws InterruptedException {
        //創(chuàng)建CountDownLatch對(duì)象，設(shè)置初始值
        CountDownLatch countDownLatch = new CountDownLatch(6);
        //6個(gè)同學(xué)陸續(xù)離開教室之后
        for (int i = 1; i <=6; i++) {
            new Thread(()->{
                System.out.println(Thread.currentThread().getName()+" 號(hào)同學(xué)離開了教室");
               //計(jì)數(shù)器減一,不會(huì)阻塞
                countDownLatch.countDown();
            },String.valueOf(i)).start();
        }
        //主線程 await 休息
        countDownLatch.await();
        //全部離開后自動(dòng)喚醒主線程   是指計(jì)數(shù)器不大于 0，然后繼續(xù)執(zhí)行 await 方法之后的語(yǔ)句。
         System.out.println("全部離開了,現(xiàn)在的計(jì)數(shù)器為" + 
        countDownLatch.getCount());
        System.out.println(Thread.currentThread().getName()+" 班長(zhǎng)鎖門走人了");
    }
}

//集齊7顆龍珠就可以召喚神龍
public class CyclicBarrierDemo {
    //創(chuàng)建固定值
    private static final int NUMBER = 7;
    public static void main(String[] args) {
        //創(chuàng)建CyclicBarrier
        CyclicBarrier cyclicBarrier =
                new CyclicBarrier(NUMBER,()->{
                    System.out.println("*****集齊7顆龍珠就可以召喚神龍");
                });
        //集齊七顆龍珠過(guò)程
        for (int i = 1; i <=7; i++) {
            new Thread(()->{
                try {
                    System.out.println(Thread.currentThread().getName()+" 星龍被收集到了");
                    //等待
                    cyclicBarrier.await();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            },String.valueOf(i)).start();
        }
    }
}

//6輛汽車，停3個(gè)車位
public class SemaphoreDemo {
    public static void main(String[] args) {
        //創(chuàng)建Semaphore，設(shè)置許可數(shù)量
        Semaphore semaphore = new Semaphore(3);
        //模擬6輛汽車
        for (int i = 1; i <=6; i++) {
            new Thread(()->{
                try {
                    //搶占
                    semaphore.acquire();
                    System.out.println(Thread.currentThread().getName()+" 搶到了車位");
                    //設(shè)置隨機(jī)停車時(shí)間
                    TimeUnit.SECONDS.sleep(new Random().nextInt(5));
                    System.out.println(Thread.currentThread().getName()+" ------離開了車位");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } finally {
                    //釋放
                    semaphore.release();
                }
            },String.valueOf(i)).start();
        }
    }
}