[Java知识库]java并发编程常用辅助类-JUC学习篇

1、CountDownLatch
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 class CountDownLatchDemo {
    public static void main(String[] args) throws InterruptedException {
        CountDownLatch countDownLatch = new CountDownLatch(6);
        for (int i = 1; i <=6; i++) {
            new Thread(()->{
                System.out.println(Thread.currentThread().getName()+"Go Out");
                countDownLatch.countDown();//-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");
    }
}

2、 CyclicBarrier减法计数器

public class CyclicBarrierDemo {
    public static void main(String[] args) {
        CyclicBarrier cyclicBarrier=new CyclicBarrier(7,()->{
            System.out.println("成功");
        });
        for (int i = 1; i <=7; i++) {
            final int temp=i;
            new Thread(()->{
                System.out.println(Thread.currentThread().getName()+"收集");
                try {
                    cyclicBarrier.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }
            }).start();
        }
    }
}

3、Semaphore:信号量

public class SemaphoreDemo {
    public static void main(String[] args) {
        Semaphore semaphore=new Semaphore(3);
        for (int i = 1; i<=6; i++) {
            new Thread(()->{
                try {
                    semaphore.acquire();
                    System.out.println(Thread.currentThread().getName()+"成功");
                    TimeUnit.SECONDS.sleep(2);
                    System.out.println(Thread.currentThread().getName() + "逃离");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }finally {
                    semaphore.release();
                }
            },String.valueOf(i)).start();
        }
    }
}

原理： semaphore.acquire() 获得，当已经满了，等待被释放为止
semaphore.release() 释放，会将当前的释放量+1，然后唤醒等待的线程!
作用:多个共享资源互斥的使用！并发限流，控制最大的线程数！

本篇文章是在哔哩哔哩听了狂神老师的JUC课程记录的笔记！方便自己查看！