CountDownLatch / CyclicBarrier / Semaphore 的介紹

CountDownLatch

讓一些線程阻塞直到另一些線程完成一系列操作後才被喚醒

package com.brian.interview.study.thread;

import com.brian.interview.enums.CountryEnum;

import java.util.concurrent.CountDownLatch;

/**
 * Copyright (c) 2020 ZJU All Rights Reserved
 * <p>
 * Project: JavaSomeDemo
 * Package: com.brian.interview.study.thread
 * Version: 1.0
 * <p>
 * Created by Brian on 2020/2/12 14:22
 */
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() + "\t 國, 被滅");
                countDownLatch.countDown();
            }, CountryEnum.forEach_CountryEnum(i).getRetMessage()).start();
        }
        countDownLatch.await();
        System.out.println(Thread.currentThread().getName() + "\t *************秦帝國, 一統華夏");

        System.out.println();
        System.out.println(CountryEnum.ONE);
        System.out.println(CountryEnum.ONE.getRetCode());
        System.out.println(CountryEnum.ONE.getRetMessage());
    }

    private static void closeDoor() throws InterruptedException {
        CountDownLatch countDownLatch = new CountDownLatch(6);

        for (int i = 1; i <= 6; i++) {
            new Thread(() -> {
                System.out.println(Thread.currentThread().getName() + "\t 上完自習, 離開教室");
                countDownLatch.countDown();
            }, String.valueOf(i)).start();
        }
        countDownLatch.await();
        System.out.println(Thread.currentThread().getName() + "\t *************班長最後關門走人");
    }
}

CyclicBarrier

集齊7顆龍珠就能召喚神龍

package com.brian.interview.study.thread;

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

/**
 * Copyright (c) 2020 ZJU All Rights Reserved
 * <p>
 * Project: JavaSomeDemo
 * Package: com.brian.interview.study.thread
 * Version: 1.0
 * <p>
 * Created by Brian on 2020/2/12 18:06
 */
public class CyclicBarrierDemo {
    public static void main(String[] args) {
        // CyclicBarrier(int parties, Runnable barrierAction)
        CyclicBarrier cyclicBarrier = new CyclicBarrier(7, () -> {System.out.println("*******召喚神龍");});

        for (int i = 1; i <= 7; i++) {
            final int tempInt = i;
            new Thread(() -> {
                System.out.println(Thread.currentThread().getName() + "\t 收集到第：" + tempInt + "龍珠");
                try {
                    cyclicBarrier.await();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (BrokenBarrierException e) {
                    e.printStackTrace();
                }
            }, String.valueOf(i)).start();
        }
    }
}

Semaphore

信號量主要用於兩個目的，一個是用於多個共享資源的互斥使用，另一個用於併發線程數的控制。

package com.brian.interview.study.thread;

import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;

/**
 * Copyright (c) 2020 ZJU All Rights Reserved
 * <p>
 * Project: JavaSomeDemo
 * Package: com.brian.interview.study.thread
 * Version: 1.0
 * <p>
 * Created by Brian on 2020/2/12 18:25
 */
public class SemaphoreDemo {
    public static void main(String[] args) {
        Semaphore semaphore = new Semaphore(3);  // 模擬3個停車位

        for (int i = 1; i <= 6; i++) {  // 模擬6部汽車
            new Thread(() -> {
                try {
                    semaphore.acquire();
                    System.out.println(Thread.currentThread().getName() + "\t搶到車位");

                    try {
                        TimeUnit.SECONDS.sleep(3);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                    System.out.println(Thread.currentThread().getName() + "\t停車3秒後離開車位");
                    semaphore.release();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } finally {

                }
            }, String.valueOf(i)).start();
        }
    }
}