JUC 常用3大辅助类

CountDownLatch

充当计数器作用 每次执行减一
使用await方法 判断必须值为0时才能下一步操作

package com.jie.add;

import java.util.concurrent.CountDownLatch;

public class CountDownLatchDemo {
    public static void main(String[] args) throws InterruptedException {
        //总数是6
        CountDownLatch countDownLatch=new CountDownLatch(6);
        //countDownLatch.countDown();//-1
        for (int i = 0; i < 6; i++) {
            new Thread(()->{
                System.out.println(Thread.currentThread().getName()+" run");
                countDownLatch.countDown();
            }).start();
        }
        countDownLatch.await();//等值为0时才能向下走
        System.out.println("运行完辣");
    }
}

CyclicBarrierTest

上面对应的减法,这个就是对应的加法

    public static void main(String[] args) {
        CyclicBarrier cyclicBarrier=new CyclicBarrier(7,()->{
            System.out.println("召唤神龙成功");
        });
        for (int i = 1; i <= 7 ; i++) {
            //lambda无法获得i
            final int temp=i;
            new Thread(()->{
                System.out.println(Thread.currentThread().getName()+" 获得了第"+temp+" 龙珠");
                try {
                    cyclicBarrier.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }
            }).start();
        }
    }

Semaphore

用与分配资源情形

    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
                //release 释放 可以理解为操作系统的PV操作
                try {
                    semaphore.acquire();
                    System.out.println(Thread.currentThread().getName()+" 抢到车位");
                    TimeUnit.SECONDS.sleep(3);
                    System.out.println(Thread.currentThread().getName()+" 离开车位");

                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                finally {
                    semaphore.release();
                }
            }).start();
        }
    }