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！