Java CountDownLatch与CyclicBarrier及Semaphore使用教程

public class CountDownLatchDemo {
    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 countDownLatch = new CountDownLatch(6);
    for (int i = 1; i <=6 ; i++) {    
        new Thread(()->{
        System.out.println(Thread.currentThread().getName()+" Go out");
        countDownLatch.countDown(); // 数量-1
        },String.valueOf(i)).start();
    }  
    countDownLatch.await(); // 等待计数器归零，然后再向下执行
    System.out.println("Close Door");
    }
}

public class CyclicBarrierDemo {
    public static void main(String[] args) {
         // 召唤龙珠的线程
        CyclicBarrier cyclicBarrier = new CyclicBarrier(7,()->{
            System.out.println("召唤神龙成功！");
        });
        for (int i = 1; i <=7 ; i++) {
            final int temp = i;
            // lambda能操作到 i 吗
            new Thread(()->{
                System.out.println(Thread.currentThread().getName()+"收集"+temp+"个龙珠");
                try {
                cyclicBarrier.await(); // 等待
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }
            }).start();
        }
    }
}

public class SemaphoreDemo {
    public static void main(String[] args) {
        // 线程数量：停车位! 限流！
        Semaphore semaphore = new Semaphore(3);
        for (int i = 1; i <=6 ; i++) {
            new Thread(()->{
            // acquire() 得到
            try {
                semaphore.acquire();
                System.out.println(Thread.currentThread().getName()+"抢到车位");
                TimeUnit.SECONDS.sleep(2);
                System.out.println(Thread.currentThread().getName()+"离开车位");
            } catch (InterruptedException e) {
                e.printStackTrace();
            } finally {
                semaphore.release(); // release() 释放
            }
        },String.valueOf(i)).start();
        }
    }
}