喜歡與改變

/*
 * Copyright (c) XXX Corp.
 * All Rights Reserved.
 */

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

/**
 * Main.
 *
 * @author Feng Yongkang, 2020/10/26
 * @version XXX v1.0
 */
public class Main {
    public static void main(String[] args) throws InterruptedException, ExecutionException {
        AlternateDemo alternateDemo = new AlternateDemo();
        new Thread(() -> {
            for (int i = 0; i < 5; i++) {
                alternateDemo.loop1();
            }
        }, "線程A").start();
        new Thread(() -> {
            for (int i = 0; i < 5; i++) {
                alternateDemo.loop2();
            }
        }, "線程B").start();
        new Thread(() -> {
            for (int i = 0; i < 5; i++) {
                alternateDemo.loop3();
            }
        }, "線程C").start();
    }
}

class AlternateDemo {
　　//交替的信號
    private int number = 1;
    private Lock lock = new ReentrantLock();
　　//多線程下控制方法跟隨信號執行
    private Condition condition1 = lock.newCondition();
    private Condition condition2 = lock.newCondition();
    private Condition condition3 = lock.newCondition();

    public void loop1() {
        lock.lock();
        try {
            if (number != 1) {
                condition1.await();
            }
            System.out.println(Thread.currentThread().getName());
            number = 2;
            condition2.signal();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    public void loop2() {
        lock.lock();
        try {
            if (number != 2) {
                condition2.await();
            }
            System.out.println(Thread.currentThread().getName());
            number = 3;
            condition3.signal();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    public void loop3() {
        lock.lock();
        try {
            if (number != 3) {
                condition3.await();
            }
            System.out.println(Thread.currentThread().getName());
            number = 1;
            condition1.signal();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
}