顺序打印数字的进一步理解

之前博客写了篇博文，面试时要求使用多线程顺序打印ABC循环20次，这是我当时使用join函数实现代码：

public class TestABCJoin {public static void main(String[] args) {// 创建任务Runnable taskA = () -> {for (int i = 0; i < 5; i++) {System.out.println(Thread.currentThread().getName() + "\t" + i);}};Runnable taskB = () -> {for (int i = 0; i < 5; i++) {System.out.println(Thread.currentThread().getName() + "\t" + i);}};Runnable taskC = () -> {for (int i = 0; i < 5; i++) {System.out.println(Thread.currentThread().getName() + "\t" + i);}};// 循环 20 次for (int i = 0; i < 20; i++) {Thread threadA = new Thread(taskA, "A");Thread threadB = new Thread(taskB, "B");Thread threadC = new Thread(taskC, "C");try {threadA.start(); // 启动 AthreadA.join();  // 等待 A 执行完毕threadB.start(); // 启动 BthreadB.join();  // 等待 B 执行完毕threadC.start(); // 启动 CthreadC.join();  // 等待 C 执行完毕} catch (InterruptedException e) {Thread.currentThread().interrupt();}}}
}

这两天复习多线程，想到condition也可以实现这个需求，先贴上代码：

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;public class TestABCLockCondition {public static void main(String[] args) {Alternate alternate = new Alternate();new Thread(() -> {for (int i = 0; i < 20; i++) {alternate.loopA(i);}}, "A").start();new Thread(() -> {for (int i = 0; i < 20; i++) {alternate.loopB(i);}}, "B").start();new Thread(() -> {for (int i = 0; i < 20; i++) {alternate.loopC(i);}}, "C").start();}
}class Alternate {private int number = 1; // 当前应执行的线程标记：1-A, 2-B, 3-Cprivate final Lock lock = new ReentrantLock();private final Condition conditionA = lock.newCondition();private final Condition conditionB = lock.newCondition();private final Condition conditionC = lock.newCondition();public void loopA(int totalLoop) {lock.lock();try {while (number != 1) {conditionA.await();}for (int i = 0; i < 5; i++) {System.out.println(Thread.currentThread().getName() + "\t" + i + "\t" + totalLoop);}number = 2;conditionB.signal();} catch (InterruptedException e) {Thread.currentThread().interrupt();} finally {lock.unlock();}}public void loopB(int totalLoop) {lock.lock();try {while (number != 2) {conditionB.await();}for (int i = 0; i < 5; i++) {System.out.println(Thread.currentThread().getName() + "\t" + i + "\t" + totalLoop);}number = 3;conditionC.signal();} catch (InterruptedException e) {Thread.currentThread().interrupt();} finally {lock.unlock();}}public void loopC(int totalLoop) {lock.lock();try {while (number != 3) {conditionC.await();}for (int i = 0; i < 5; i++) {System.out.println(Thread.currentThread().getName() + "\t" + i + "\t" + totalLoop);}number = 1;conditionA.signal();} catch (InterruptedException e) {Thread.currentThread().interrupt();} finally {lock.unlock();}}
}