线程按序交替

编写一个程序，开启 3 个线程，这三个线程的 ID 分别为 A、B、C，

每个线程将自己的 ID 在屏幕上打印 10 遍，要 求输出的结果必须按顺序显示

TestABCAlternate

package com.aff.juc;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class TestABCAlternate {
    public static void main(String[] args) {
        AlternateDemo ad = new AlternateDemo();
        new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 1; i <= 20; i++) {
                    ad.loopA(i);
                }
            }
        },"A线程").start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 1; i <= 20; i++) {
                    ad.loopB(i);
                }
            }
        },"B线程").start();
        new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 1; i <=20; i++) {
                    ad.loopC(i);
                    System.out.println("=============================");
                }
            }
        },"C线程").start();

    }
}

class AlternateDemo {
    private int number = 1;
    private Lock lock = new ReentrantLock();
    private Condition condition1 = lock.newCondition();
    private Condition condition2 = lock.newCondition();
    private Condition condition3 = lock.newCondition();

    // totalLoop :循环几轮
    public void loopA(int totalLoop) {
        lock.lock();
        try {
            // 1. 判断
            if (number != 1) {
                condition1.await();
            }
            // 2.打印
            for (int i = 1; i <= 2; i++) {
                System.out.println(Thread.currentThread().getName() +                                          "\t" + i +"\t"+ "\t" + totalLoop);
            }
            // 3.唤醒
            number = 2;
            condition2.signal();// number为2 唤醒condition2

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    public void loopB(int totalLoop) {
        lock.lock();
        try {
            // 1. 判断
            if (number != 2) {
                condition2.await();
            }
            // 2.打印
            for (int i = 1; i <= 2; i++) {
                System.out.println(Thread.currentThread().getName() +                                         "\t" + "\t"+ i + "\t" + totalLoop);
            }
            // 3.唤醒
            number = 3;
            condition3.signal();// number为3 唤醒condition3

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    public void loopC(int totalLoop) {
        lock.lock();
        try {
            // 1. 判断
            if (number != 3) {
                condition3.await();
            }
            // 2.打印
            for (int i = 1; i <= 2; i++) {
                System.out.println(Thread.currentThread().getName() +                                          "\t" + "\t"+ i + "\t" + totalLoop);
            }
            // 3.唤醒
            number = 1;
            condition1.signal();// number为1 唤醒condition1

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

}

 

来源：https://www.cnblogs.com/afangfang/p/12632559.html