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

 1 public class CyclicBarrierDemo {
 2     public static void main(String[] args) {
 3         //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
 4         CyclicBarrier barrier = new CyclicBarrier(9,()->{
 5             System.out.println("召唤神龙耶");
 6         });
 7 
 8 
 9         for (int i = 0; i <=7; i++) {
10             int temp = i;
11             //lambda能操作  i 吗
12             new Thread(()->{
13                 System.out.println(Thread.currentThread().getName()+"收集"+temp+"个龙珠");
14                 try {
15                     barrier.await();
16                 } catch (InterruptedException e) {
17                     e.printStackTrace();
18                 } catch (BrokenBarrierException e) {
19                     e.printStackTrace();
20                 }
21             }).start();
22         }
23     }
24 }

Semaphore

 1 public class SemahoreDome {
 2     public static void main(String[] args) {
 3         //线程数量,停车位  限流会用到
 4 
 5         Semaphore semaphore = new Semaphore(3);
 6 
 7         for (int i = 0; i <=6; i++) {
 8             new Thread(()->{
 9                 //acquire()得到
10                 try {
11                     semaphore.acquire();
12                     System.out.println(Thread.currentThread().getName()+"得到 车位");
13                     TimeUnit.SECONDS.sleep(2);
14                     System.out.println(Thread.currentThread().getName()+"离开停车场");
15                 } catch (InterruptedException e) {
16                     e.printStackTrace();
17                 }finally {
18                     semaphore.release();//release() 释放
19                 }
20             },String.valueOf(i)).start();
21         }
22 
23     }
24 }