Java中CountDownLatch工具类详细解析

Java中CountDownLatch工具类详细解析

创建CountDownLatch对象时，会传入一个count数值，该对象每次调用countDown()方法会使count -- ，就是count每次减1; 调用await()方法，程序会阻塞等待，当count被减到0了之后，await()后面的程序解除阻塞，可以继续运行。 阻塞的是调用await()方法的后续代码，调用countDown()方法count自减1，当count=0 时解除阻塞。 如:

CountDownLatch countDownLatch = new CountDownLatch(4); //初始 count = 4python
countDownLatch.countDown(); // count = 4 -1;
countDownLatch.countDown();  // count = 3-1;
countDownLatch.await(); //当count =0 ，可以执行后续代码

代码示例1: 当count不为0时，程序会一直等待。

import java.util.concurrent.CountDownLatch;

public class Test {

    public static void main(String[] args) throws InterruptedException {
        CountDownLatch countDownLatch = new CountDownLatch(5);

        new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println(Thread.currentThread().getName()+"已运行!");
                countDownLatch.countDown();
            }
        }).start();

        countDownLatch.await();
        System.out.println(" 程序执行完毕! ");
    }
}

代码示例2：count=0解除阻塞。

import java.util.concurrent.CountDownLatch;

public class Test1 {

    public static void main(String[] args) throws InterruptedException {
        CountDownLatch countDownLatch = new CountDownLatch(5);
        for(int i = 0 ; i < 5 ; i++){
            new Thread(new Runnable() {
    编程客栈            @Override
                public void run() {
                    System.out.println(Thread.currentThread().getName()+"已运行!");
                    javascriptcountDownLatch.countDown();
                }
            }).start();
        }


        countDownLatch.await();
        System.out.println(" 程序执行完毕! ");
    }
}

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