1:CyclicBarrier类说明
一个同步辅助类,它允许一组线程互相等待,直到到达某个公共屏障点 (common barrier point)。在涉及一组固定大小的线程的程序中,这些线程必须不时地互相等待,此时
CyclicBarrier 很有用。因为该 barrier 在释放等待线程后可以重用,所以称它为循环 的 barrier
2:使用场景
需要所有的子任务都完成时,才执行主任务,这个时候就可以选择使用CyclicBarrier
3:查看api
现在写一个demo玩下,
package cn.kge.com.thread; import java.io.IOException; import java.util.Random; import java.util.concurrent.BrokenBarrierException; import java.util.concurrent.CyclicBarrier; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class CyclicBarrierTest { public static void main(String[] args) throws IOException, InterruptedException { //如果将参数改为4,但是下面只加入了3个选手,这永远等待下去 //Waits until all parties have invoked await on this barrier. CyclicBarrier barrier = new CyclicBarrier(4); ExecutorService executor = Executors.newFixedThreadPool(4); executor.submit(new Thread(new Runner(barrier, "张三"))); executor.submit(new Thread(new Runner(barrier, "李四"))); executor.submit(new Thread(new Runner(barrier, "王五"))); executor.submit(new Thread(new Runner(barrier, "老刘"))); executor.shutdown(); } } class Runner implements Runnable { // 一个同步辅助类,它允许一组线程互相等待,直到到达某个公共屏障点 (common barrier point) private CyclicBarrier barrier; private String name; public Runner(CyclicBarrier barrier, String name) { super(); this.barrier = barrier; this.name = name; } @Override public void run() { try { Thread.sleep(1000 * (new Random()).nextInt(8)); System.out.println(name + " 马上到..."); // barrier的await方法,在所有参与者都已经在此 barrier 上调用 await 方法之前,将一直等待。 barrier.await(); } catch (InterruptedException e) { e.printStackTrace(); } catch (BrokenBarrierException e) { e.printStackTrace(); } System.out.println("一起泡妞去"); } }