/**
* 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();
}
}
