3个线程顺序打印1-100的值

package problem;

import java.util.concurrent.locks.ReentrantLock;

/**
 * @Autor HumgTop
 * @Date 2021/5/26 9:35
 * @Version 1.0
 * 3个线程顺序打印数字 1-100
 */
public class ShunXuDaYin1_100DeZhi {
    static int num = 0;
    static ReentrantLock lock = new ReentrantLock();

    public static void main(String[] args) {
        new MyThread(0).start();
        new MyThread(1).start();
        new MyThread(2).start();
    }

    static class MyThread extends Thread {
        int tag;    //线程标记号，用于顺序同步

        public MyThread(int tag) {
            this.tag = tag;
        }

        @Override
        public void run() {
            while (num < 100) {
                //双重检查锁定：避免其他线程在num<100时进入while循环，然后阻塞。等到取到锁时，num已经大于100。如果不作二次检查，会导致打印出大于100的值。
                lock.lock();
                //取模运算保证线程打印的顺序
                if (num < 100 && num % 3 == tag) {
                    System.out.print(Thread.currentThread());
                    num++;
                    System.out.print(num + "\n");
                }
                lock.unlock();
            }
        }
    }
}