使用3个线程依次打印 ABC

最新推荐文章于 2024-02-22 15:34:59 发布

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本文介绍了一个使用Java实现的多线程同步问题解决方案。通过三个线程A、B、C循环打印字符，确保输出顺序正确且同步进行。利用ReentrantLock和Condition实现了精确的线程控制。

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转载自尚硅谷官网例子

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();
}
}

}