Thinking in Java学习笔记 CountDownLatch（CountDownLatchDemo.java）

CountDownLatchDemo.java

每个任务线程完成一部分工作，完成后通过CountDownLatch来通知总线程，

总线程通过CountDownLatch.await()等待所有子线程完成操作后，再结束

package com.test.concurrent;

import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

public class CountDownLatchDemo {
	static final int SIZE=100;
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		ExecutorService exec=Executors.newCachedThreadPool();
		CountDownLatch latch=new CountDownLatch(SIZE);
		for(int i=0;i<10;i++){
			exec.execute(new WaitingTask(latch));
		}
		for(int i=0;i<SIZE;i++){
			exec.execute(new TaskPortion(latch));
		}
		System.out.println("Launched all tasks");
		exec.shutdown();
		
	}

}

class TaskPortion implements Runnable{
	private static int counter=0;
	private final int id=counter++;
	private static Random rand=new Random(47);
	private final CountDownLatch latch;
	TaskPortion(CountDownLatch latch){
		this.latch=latch;
	}
	public void dowork() throws InterruptedException{
		TimeUnit.MILLISECONDS.sleep(rand.nextInt(2000));
		System.out.println(this+" is completed!");
	}
	@Override
	public void run() {
		// TODO Auto-generated method stub
		try {
			dowork();
			latch.countDown();
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	public String toString(){
		return "Task Portion id:"+id;
	}
	
}
class WaitingTask implements Runnable{
	private static int counter=0;
	private final int id=counter++;
	private final CountDownLatch latch;
	WaitingTask(CountDownLatch latch){
		this.latch=latch;
	}
	public String toString(){
		return "Waiting Task id:"+id;
	}
	@Override
	public void run(){
		try {
			latch.await();
			System.out.println("Latch barrier passed for "+this);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
}