计数器设计模式CountDown设计模式

计数器设计模式CountDown设计模式 当多个线程在执行完成时，要等待 一起提交结果 ，可以用join实现

JDK自带的CountDownLatch 很容易的实现了这一个功能，先看jdk怎么实现的

package com.thread.ch14;

import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.stream.IntStream;

public class JdkCountDown {
    private static final Random random = new Random(System.currentTimeMillis());

    public static void main(String[] args) throws InterruptedException {
        CountDownLatch latch = new CountDownLatch(4);
        //第一步線程操作
        IntStream.range(1, 5).forEach(i -> {
            new Thread(() -> {
                System.out.println(Thread.currentThread().getName() + " is working");
                try {
                    Thread.sleep(random.nextInt(1000));
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                latch.countDown();
            },String.valueOf(i)).start();
        });
        latch.await();
        //第二部提交結果
        System.out.println("多线程任务全部结束,准备第二阶段任务");
        System.out.println("............");
        System.out.println("FINISH");
    }
}

打印结果:

1 is working
2 is working
4 is working
3 is working
多线程任务全部结束,准备第二阶段任务
............
FINISH

自己是实现一个countDown

package com.thread.ch14;

public class CountDown {
    //次數
    private int count = 1;
    //總次數
    private int total;

    public CountDown(int total) {
        this.total = total;
    }

    public void down() {
        synchronized (this) {
            this.count++;
            System.out.println("down-----"+Thread.currentThread().getName());
            this.notifyAll();
        }
    }

    public void await() throws InterruptedException {
        synchronized (this) {
            while (count <= total) {
                this.wait();
            }
        }
    }
}

package com.thread.ch14;

import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.stream.IntStream;

public class CountDownClient {
    private static final Random random = new Random(System.currentTimeMillis());

    public static void main(String[] args) throws InterruptedException {
        CountDown latch = new CountDown(4);
        //第一步線程操作
        IntStream.range(1, 5).forEach(i -> {
            new Thread(() -> {
                System.out.println(Thread.currentThread().getName() + " is working");
                try {
                    Thread.sleep(random.nextInt(1000));
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                latch.down();
            },String.valueOf(i)).start();
        });
        latch.await();
        //第二部提交結果
        System.out.println("多线程任务全部结束,准备第二阶段任务");
        System.out.println("............");
        System.out.println("FINISH");
    }
}

打印结果一样

1 is working
2 is working
4 is working
3 is working
down-----4
down-----2
down-----1
down-----3
多线程任务全部结束,准备第二阶段任务
............
FINISH
 

 

 

来源：oschina

链接：https://my.oschina.net/lvzi98/blog/3170848