面试题：多线程打印ABC

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

public class ABC_Lock {
    
    
    private static Lock lock = new ReentrantLock();// 通过JDK5中的Lock锁来保证线程的访问的互斥
    private static int state = 0;//通过state的值来确定是否打印

    static class ThreadA extends Thread {
    
    
        @Override
        public void run() {
    
    
            for (int i = 0; i < 10;) {
    
    
                try {
    
    
                    lock.lock();
                    while (state % 3 == 0) {
    
    // 多线程并发，不能用if，必须用循环测试等待条件，避免虚假唤醒
                        System.out.print("A");
                        state++;
                        i++;
                    }
                } finally {
    
    
                    lock.unlock();// unlock()操作必须放在finally块中
                }
            }
        }
    }

    static class ThreadB extends Thread {
    
    
        @Override
        public void run() {
    
    
            for (int i = 0; i < 10;) {
    
    
                try {
    
    
                    lock.lock();
                    while (state % 3 == 1) {
    
    // 多线程并发，不能用if，必须用循环测试等待条件，避免虚假唤醒
                        System.out.print("B");
                        state++;
                        i++;
                    }
                } finally {
    
    
                    lock.unlock();// unlock()操作必须放在finally块中
                }
            }
        }
    }

    static class ThreadC extends Thread {
    
    
        @Override
        public void run() {
    
    
            for (int i = 0; i < 10;) {
    
    
                try {
    
    
                    lock.lock();
                    while (state % 3 == 2) {
    
    // 多线程并发，不能用if，必须用循环测试等待条件，避免虚假唤醒
                        System.out.print("C");
                        state++;
                        i++;
                    }
                } finally {
    
    
                    lock.unlock();// unlock()操作必须放在finally块中
                }
            }
        }
    }

    public static void main(String[] args) {
    
    
        new ThreadA().start();
        new ThreadB().start();
        new ThreadC().start();
    }
}

来自：https://blog.csdn.net/xiaokang123456kao/article/details/77331878