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) {
final AlternateDemo ad = new AlternateDemo();
new Thread(new Runnable() {
@Override
public void run() {
for (int i = 0; i < 10; i++) {
ad.loopA();
}
}
}, "A").start();
new Thread(new Runnable() {
@Override
public void run() {
for (int i = 0; i < 10; i++) {
ad.loopB();
}
}
}, "B").start();
new Thread(new Runnable() {
@Override
public void run() {
for (int i = 0; i < 10; i++) {
ad.loopC();
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();
public void loopA() {
lock.lock();
try {
//1. 判断
if (number != 1) {
condition1.await();
}
//2. 打印
System.out.println(Thread.currentThread().getName());
//3. 唤醒
number = 2;
condition2.signal();
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
public void loopB() {
lock.lock();
try {
//1. 判断
if (number != 2) {
condition2.await();
}
//2. 打印
System.out.println(Thread.currentThread().getName());
//3. 唤醒
number = 3;
condition3.signal();
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
public void loopC() {
lock.lock();
try {
//1. 判断
if (number != 3) {
condition3.await();
}
//2. 打印
System.out.println(Thread.currentThread().getName());
//3. 唤醒
number = 1;
condition1.signal();
} catch (Exception e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
}
