java-多线程面试题：同时运行ABC三个线程，依次输出ABC，最终结果为ABCABCABCABC

package com.cc.thread;

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

/**
 * 面试题：同时运行ABC三个线程，依次输出ABC，最终结果为ABCABCABCABC...
 */
public class PrintLock3 {
    public static void main(String[] args) {

        ShareData3 shareData = new ShareData3();
        new Thread(() -> {//线程A循环5次
            for (int i = 0; i < 5; i++) {
                shareData.printA();//调用资源类打印A方法
            }
        }, "A").start();
        new Thread(() -> {//线程B循环5次
            for (int i = 0; i < 5; i++) {
                shareData.printB();//调用资源类打印B方法
            }
        }, "B").start();
        new Thread(() -> {//线程C循环5次
            for (int i = 0; i < 5; i++) {
                shareData.printC();//调用资源类打印C方法
            }
        }, "C").start();
    }

}

//资源类
class ShareData3{
    private int flag = 1;
    Lock lock = new ReentrantLock();
    Condition condition = lock.newCondition();

    public void printA(){
        lock.lock();
        try {
            while(flag != 1){//如果flag不为1，则等待，为偶数则输出，然后设置flag为2并通知唤醒其他线程
                condition.await();
            }
            System.out.println(Thread.currentThread().getName() + "输出数：A");
            flag = 2;
            condition.signalAll();
        }
        catch (Exception e){
            e.printStackTrace();
        }
        finally {
            lock.unlock();
        }
    }

    public void printB(){
        lock.lock();
        try {
            while(flag != 2){//如果flag不为2，则等待，为偶数则输出，然后设置flag为3并通知唤醒其他线程
                condition.await();
            }
            System.out.println(Thread.currentThread().getName() + "输出数：B");
            flag = 3;
            condition.signalAll();
        }
        catch (Exception e){
            e.printStackTrace();
        }
        finally {
            lock.unlock();
        }
    }

    public void printC(){
        lock.lock();
        try {
            while(flag != 3){//如果flag不为3，则等待，为偶数则输出，然后设置flag为1并通知唤醒其他线程
                condition.await();
            }
            System.out.println(Thread.currentThread().getName() + "输出数：C");
            flag = 1;
            condition.signalAll();
        }
        catch (Exception e){
            e.printStackTrace();
        }
        finally {
            lock.unlock();
        }
    }
}