经典多线程问题（五）-按顺序执行的问题

package com.example.demo;

import java.util.concurrent.CountDownLatch;

/**
 * @ClassName Foo
 * @Description: 1114. 按序打印(多线程)
 * @Author xtanb
 * @Date 2019/9/23
 * @Version V1.0
 **/
public class Foo {
    private CountDownLatch countDownLatchA;
    private CountDownLatch countDownLatchB;

    public Foo() {
        this.countDownLatchA = new CountDownLatch(1);
        this.countDownLatchB = new CountDownLatch(1);
    }

    public void first(Runnable printFirst) throws InterruptedException {

        // printFirst.run() outputs "first". Do not change or remove this line.
        printFirst.run();
        countDownLatchA.countDown();
    }

    public void second(Runnable printSecond) throws InterruptedException {
        countDownLatchA.await();
        // printSecond.run() outputs "second". Do not change or remove this line.
        printSecond.run();
        countDownLatchB.countDown();
    }

    public void third(Runnable printThird) throws InterruptedException {
        countDownLatchB.await();
        // printThird.run() outputs "third". Do not change or remove this line.
        printThird.run();
    }
}