JUC种常用的辅助类

小半 • 2023年1月10日下午2:49 • 技术随笔 • 阅读 136

常用的辅助类

在JUC并发编程里面，有一个常用的辅助类；
java.util.concurrent 包下的；

1：CountDownLatch

这是一个一次性的现象 – 计数无法重置。

package com.baidu.add;

import java.util.concurrent.CountDownLatch;

public class CountDownLatchDemo {
    //相当与我们的减法操作

    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()+"Get Out");
                countDownLatch.countDown(); //数量减一1
            },String.valueOf(i)).start();
        }

        countDownLatch.await(); //等待计数器为零 ,然后在往下执行;

        System.out.println("Close Door");
    }

}

原理：
countDownLatch.countDown(); //数量减一1
countDownLatch.await(); //等待计数器为零 ,然后在往下执行;

2：CyclicBarrier

释放之后重新使用。

package com.baidu.add;

import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;

public class CyclicBarrierDemo {

    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++) {

            final int temp = i;
            new Thread(()->{
                System.out.println(Thread.currentThread().getName()+"收集"+temp+"个龙珠.");

                try {
                    cyclicBarrier.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }
            }).start();
        }
    }
}

3：Semaphore

package com.baidu.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.限流!!
        Semaphore semaphore = new Semaphore(3);

        for (int i = 1; i <= 6; i++) {
           new Thread(()->{
               //acquire()得到
               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 {
                   //release()释放
                   semaphore.release();
               }
           },String.valueOf(i)).start();
        }
    }
}