GUC-8 小练习

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

/*
 * 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。
 *    如：ABCABCABC…… 依次递归
 */
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").start();

        new Thread(new Runnable() {
            @Override
            public void run() {

                for (int i = 1; i <= 20; i++) {
                    ad.loopB(i);
                }

            }
        }, "B").start();

        new Thread(new Runnable() {
            @Override
            public void run() {

                for (int i = 1; i <= 20; i++) {
                    ad.loopC(i);

                    System.out.println("-----------------------------------");
                }

            }
        }, "C").start();
    }

}

class AlternateDemo{

    private int number = 1; //当前正在执行线程的标记

    private Lock lock = new ReentrantLock();
    private Condition condition1 = lock.newCondition();
    private Condition condition2 = lock.newCondition();
    private Condition condition3 = lock.newCondition();

    /**
     * @param totalLoop : 循环第几轮
     */
    public void loopA(int totalLoop){
        lock.lock();

        try {
            //1. 判断
            if(number != 1){
                condition1.await();
            }

            //2. 打印
            for (int i = 1; i <= 1; i++) {
                System.out.println(Thread.currentThread().getName() + "\t" + i + "\t" + totalLoop);
            }

            //3. 唤醒
            number = 2;
            condition2.signal();
        } 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 <= 1; i++) {
                System.out.println(Thread.currentThread().getName() + "\t" + i + "\t" + totalLoop);
            }

            //3. 唤醒
            number = 3;
            condition3.signal();
        } 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 <= 1; i++) {
                System.out.println(Thread.currentThread().getName() + "\t" + i + "\t" + totalLoop);
            }

            //3. 唤醒
            number = 1;
            condition1.signal();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

}