交替打印奇偶数

/**

* 交替打印奇偶数

* 用condition来做信号量实现奇数偶数的交替打印

* @author wanghao

* @date 2018年12月25日

*/

import java.util.concurrent.locks.Condition;

import java.util.concurrent.locks.Lock;

import java.util.concurrent.locks.ReentrantLock;

public class NumberPrint {

private int index;

private Lock lock = new ReentrantLock();

private Condition oddConditon = lock.newCondition();

private Condition evenCondition = lock.newCondition();

public void printOdd() throws InterruptedException {

lock.lock();

try {

while (index < 1000) {

if (index % 2 == 0)

oddConditon.await();

System.out.println(Thread.currentThread().getName() + ":" + index++);

evenCondition.signal();

}

} finally {

lock.unlock();

}

}

/**

* 举例。如果到了999，偶数线程await，奇数线程不论之前被signal之后抢占到了锁还是evenCondition.await让出了锁，都能获得执行的权限，打印1000

* @throws InterruptedException

*/

public void printEven() throws InterruptedException {

lock.lock();

try {

while (index < 1000) {

if (index % 2 == 1)

evenCondition.await();

System.out.println(Thread.currentThread().getName() + ":" + index++);

oddConditon.signal();

}

} finally {

lock.unlock();

}

}

public static void main(String[] args) {

NumberPrint numberPrint = new NumberPrint();

Thread thread1 = new Thread(() -> {try {

numberPrint.printOdd();

} catch (InterruptedException e) {

e.printStackTrace();

}});

thread1.setName("odd thread");

Thread thread2 = new Thread(() -> {try {

numberPrint.printEven();

} catch (InterruptedException e) {

e.printStackTrace();

}});

thread2.setName("eve thread");

thread2.start();

thread1.start();

}

}