常用的辅助类(必会)

1.CountDownLatch

package com.kuang.add;import java.util.concurrent.CountDownLatch;//计数器  减法
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 = 0; i < 6; i++) {int finalI = i;new Thread(()->{try {System.out.println(Thread.currentThread().getName()+" Go Out");} catch (Exception e) {e.printStackTrace();} finally {countDownLatch.countDown();}},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

package com.kuang.add;import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;public class CyclicBarrierDemo {public static void main(String[] args) {/*** 集齐7颗龙珠 召唤神龙*///召唤龙珠的线程CyclicBarrier cyclicBarrier= new CyclicBarrier(7,()->{System.out.println("召唤神龙成功");});for (int i = 0; i < 6; i++) {int finalI = i;new Thread(()->{System.out.println(Thread.currentThread().getName()+"收集了"+ finalI+"个龙珠");try {cyclicBarrier.await();//等待} catch (InterruptedException e) {e.printStackTrace();} catch (BrokenBarrierException e) {e.printStackTrace();}}).start();}}}

 

3.Semaphore

Semaphore ：信号量

package com.kuang.add;import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;public class SemaphoreDemo {public static void main(String[] args) {//线程数量，停车位！Semaphore semaphore = new Semaphore(3);for (int i = 0; i < 6; i++) {new Thread(()->{//acquire()得到许可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();}}
}

原理：

semaphore.acquire(); 获得，假设如果已经满了，等待，等待被释放为止！

semaphore.release(); 释放，会将当前的信号量释放+1，然后唤醒等待线程！

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！