多线程之间按顺序调用，实现A->B->C三个线程启动（使用Lock锁）

题目：多线程之间按顺序调用，实现A->B->C三个线程启动，要求如下：

• AA打印5次，BB打印10次，CC打印15次
• …来十轮

思路：使用Lock锁的多个Condition实现精准唤醒。

package com.bestqiang.thread.Queue;

/**
 * @author BestQiang
 */

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

/**
 * 题目：多线程之间按顺序调用，实现A->B->C三个线程启动，要求如下：
 * AA打印5次，BB打印10次，CC打印15次
 * 然后
 * AA打印5次，BB打印10次，CC打印15次
 * ...来十轮
 */
public class SyncAndReentrantLockDemo {
    public static void main(String[] args) {
        ShareResource shareResource = new ShareResource();
        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                shareResource.print5();
            }
        }, "线程1：").start();
        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                shareResource.print10();
            }
        }, "线程2：").start();
        new Thread(() -> {
            for (int i = 0; i < 10; i++) {
                shareResource.print15();
            }
        }, "线程3：").start();
    }

}

class ShareResource {
    private int number = 1; // A:1 B:2 C:3
    private Lock lock = new ReentrantLock();
    Condition c1 = lock.newCondition();
    Condition c2 = lock.newCondition();
    Condition c3 = lock.newCondition();

    public void print5() {
        try {
            lock.lock();
            while (number != 1) {
                c1.await();
            }
            for (int i = 0; i < 5; i++) {
                System.out.println("AA");
            }
            number = 2;
            c2.signal();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    public void print10() {
        try {
            lock.lock();
            while (number != 2) {
                c2.await();
            }
            for (int i = 0; i < 10; i++) {
                System.out.println("BB");
            }
            number = 3;
            c3.signal();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    public void print15() {
        try {
            lock.lock();
            while (number != 3) {
                c3.await();
            }
            for (int i = 0; i < 15; i++) {
                System.out.println("CC");
            }
            number = 1;
            c1.signal();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
}