使用3个线程依次打印 ABC

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();
}
}

}