Java并发系列之CountDownLatch 学习

一、浩句

看看星空，会觉得自己很渺小，可能我们在宇宙中从来就是一个偶然。所以，无论什么事情，仔细想一想，都没有什么大不了的。这能帮助自己在遇到挫折时稳定心态，想得更开

二、背景

CountDownLatch 用于控制线程时序性，个人理解线程时序性即是线程的执行顺序。

三、code

CountDownLatch 使用，可以控制线程，等待其他线程执行完在继续往下执行，这是其中的一种实现方式之一

package com.mouse.moon.countDownLatch;
import java.util.concurrent.CountDownLatch;
public class Cat implements Runnable{
    private final CountDownLatch count ;
    
    public Cat(int num){
        count = new CountDownLatch(num);
    }
    
    public void eat(String name){
        System.out.println("吃了。。。。"+name);
        count.countDown();
        System.out.println("还有剩余的数量------->"+count.getCount());
    }
    
    @Override
    public void run() {
        System.out.println("count的开始大小="+count.getCount());
        try {
            count.await();
            System.out.println("到cat吃饭了,只剩渣了！！！");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

package com.mouse.moon.countDownLatch;
import java.util.concurrent.TimeUnit;
public class Dog implements Runnable {
    private Cat cat;
    private String foodName;
    
    public Dog(Cat cat,String foodName){  
        this.cat = cat;  
        this.foodName = foodName;  
    }  
    
    @Override
    public void run() {
        long duration = (long)(Math.random()*10);
        try {
            TimeUnit.SECONDS.sleep(duration);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        cat.eat(foodName);
    }
}

package com.mouse.moon.countDownLatch;
public class AppMain {
    public static void main(String args[]){
        Cat cat =new Cat(5);
        Thread thread = new Thread(cat);
        thread.start();
        for(int i=0;i < 5;i++){
            Dog dog =new Dog(cat,"food--"+i);
            Thread dogThread = new Thread(dog);
            dogThread.start();
        }
    }
}

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count.await();调用后，将等待其他全部执行完。初始化的时候初始化大小，然后在每次执行完后count.countDown()就会减1;直到为0，则将唤醒素有count.await()等待线程将继续执行。