JAVA 同步器CountDownLatch CyclicBarrier

CountDownLatch

可以实现类似计数器的功能，一般用于某个线程等待若干个其他线程执行完任务之后，它才执行

CyclicBarrier

一组线程互相等待至某个状态，然后这一组线程再同时执行

CountDownLatch例子

import java.util.concurrent.CountDownLatch;

public class JavaCountDownLatch {

public static void main(String[] args) throws InterruptedException {
CountDownLatch countDownLatch = new CountDownLatch(5);
for (int i = 0; i < 5; i++)
new JavaCountDownLatch.Student(countDownLatch, i).start();
System.out.println("等待所有同学到达");
countDownLatch.await();
System.out.println("所有同学到达目的地");

}

static class Student extends Thread {
private CountDownLatch countDownLatch;
private int id;

public Student(CountDownLatch countDownLatch, int id) {
this.countDownLatch = countDownLatch;
this.id = id;
}

public void run() {
try {
System.out.println("student " + id + "出发");
Thread.sleep(3000);
System.out.println("student " + id + "到达");
countDownLatch.countDown();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}

执行结果：

student 0出发

等待所有同学到达

student 2出发

student 4出发

student 1出发

student 3出发

student 0到达

student 2到达

student 4到达

student 1到达

student 3到达

所有同学到达目的地

CyclicBarrier例子

import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;

public class JavaCyclicBarrier {
public static void main(String[] args) {
// TODO Auto-generated method stub
CyclicBarrier cyclicBarrier = new CyclicBarrier(5);
for (int i = 0; i < 5; i++)
new JavaCyclicBarrier.Student(cyclicBarrier, i).start();
}

static class Student extends Thread {
private CyclicBarrier cyclicBarrier;
private int id;
public Student(CyclicBarrier cyclicBarrier, int id) {
this.cyclicBarrier = cyclicBarrier;
this.id = id;
}
public void run() {
try {
System.out.println("student " + id + "出发");
Thread.sleep(3000);
System.out.println("student " + id + "到达,等待其他同学");
cyclicBarrier.await();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (BrokenBarrierException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("所有同学到达目的地");
}
}
}

执行结果：

student 1出发

student 3出发

student 0出发

student 2出发

student 4出发

student 3到达,等待其他同学

student 1到达,等待其他同学

student 0到达,等待其他同学

student 2到达,等待其他同学

student 4到达,等待其他同学

所有同学到达目的地

所有同学到达目的地

所有同学到达目的地

所有同学到达目的地

所有同学到达目的地

参考资料

http://www.cnblogs.com/dolphin0520/p/3920397.html

http://blog.csdn.net/mazhimazh/article/details/19190241