常用的辅助类(必会

CountDownLatch

public class CountDownLatchDemo {
    //原理：
    //countDownLatch.countDown(); // 数量-1
    //countDownLatch.await(); // 等待计数器归零，然后再向下执行
    //每次有线程调用 countDown() 数量-1，假设计数器变为0，countDownLatch.await() 就会被唤醒，继续 执行！

    public static void main(String[] args) throws InterruptedException {
        //总数是6,必须要执行任务的时候，再使用

        CountDownLatch count = new CountDownLatch(6);

        for (int i = 0; i <=6; i++) {
            new Thread(()->{
                System.out.println(Thread.currentThread().getName()+"Go out");
                count.countDown();//数量减一
                },String.valueOf(i)).start();
        }

        count.await();//等待计数器归0,然后再向下执行
        System.out.println("Close Door");
//        count.countDown();
    }
}

CyclicBarrier

public class CyclicBarrierDemo {
    public static void main(String[] args) {
        //如果设置的数比循环里面的数大,循环里面的不满足就会卡在barrier.await();等待这里
        CyclicBarrier barrier = new CyclicBarrier(9,()->{
            System.out.println("召唤神龙耶");
        });


        for (int i = 0; i <=7; i++) {
            int temp = i;
            //lambda能操作  i 吗
            new Thread(()->{
                System.out.println(Thread.currentThread().getName()+"收集"+temp+"个龙珠");
                try {
                    barrier.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }
            }).start();
        }
    }
}

Semaphore

public class SemahoreDome {
    public static void main(String[] args) {
        //线程数量,停车位  限流会用到

        Semaphore semaphore = new Semaphore(3);

        for (int i = 0; i <=6; i++) {
            new Thread(()->{
                //acquire()得到
                try {
                    semaphore.acquire();
                    System.out.println(Thread.currentThread().getName()+"得到 车位");
                    TimeUnit.SECONDS.sleep(2);
                    System.out.println(Thread.currentThread().getName()+"离开停车场");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }finally {
                    semaphore.release();//release() 释放
                }
            },String.valueOf(i)).start();
        }

    }
}