Java并发和多线程4：使用通用同步工具CountDownLatch实现线程等待

class Driver {
	void start() throws InterruptedException {
		CountDownLatch startSignal = new CountDownLatch(1);
		int N = 5;
		CountDownLatch doneSignal = new CountDownLatch(N);


		for (int i = 0; i < N; i++) {
			Worker worker = new Worker(startSignal, doneSignal,i);
			Thread thread = new Thread(worker);
			thread.start();
		}


		doSomethingElse(1); // 所有线程都还没有开始执行
		startSignal.countDown(); // 让所有线程开始执行
		doSomethingElse(2);
		doneSignal.await(); // 等待所有线程结束
		doSomethingElse(3);
	}


	// 执行一些其它的事情，具体结合实际情况
	private void doSomethingElse(int i) {
		System.out.println("doSomethingElse-"+i);
	}
}


class Worker implements Runnable {
	private final CountDownLatch startSignal;
	private final CountDownLatch doneSignal;
	private final int i;
	Worker(CountDownLatch startSignal, CountDownLatch doneSignal,int i) {
		this.startSignal = startSignal;
		this.doneSignal = doneSignal;
		this.i=i;
	}


	public void run() {
		try {
			startSignal.await();
			doWork(i);
			doneSignal.countDown();
		} catch (InterruptedException ex) {
			ex.printStackTrace();
		}
	}


	void doWork(int i) {
		System.out.println("doWork-"+i);
	}
}

class Driver2 {
	void start() throws InterruptedException {
		int N = 5;
		CountDownLatch doneSignal = new CountDownLatch(N);
		ExecutorService e = Executors.newFixedThreadPool(3);
		// 创建并执行线程
		for (int i = 0; i < N; ++i) {
			WorkerRunnable workerRunnable = new WorkerRunnable(doneSignal, i);
			e.execute(workerRunnable);
		}
		// 等待所有线程结束
		doneSignal.await();
		//手动关闭，才会停止所有线程
		e.shutdown();
	}
}


class WorkerRunnable implements Runnable {
	private final CountDownLatch doneSignal;
	private final int i;


	WorkerRunnable(CountDownLatch doneSignal, int i) {
		this.doneSignal = doneSignal;
		this.i = i;
	}


	public void run() {
		doWork(i);
		doneSignal.countDown();
	}


	void doWork(int i) {
		System.out.println("doWork-" + i);
	}
}

package cn.fansunion.executorframework;


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




public class CountDownLatchDemo {


	public static void main(String[] args) throws InterruptedException {
		//Driver中的若干Thread，执行完毕后，自动就关闭了
		Driver driver = new Driver();
		driver.start();
		//Driver2中，需要手动调用ExecutorService.shutdown关闭线程
		Driver2 driver2 = new Driver2();
		driver2.start();
	}


}

Java并发和多线程4：使用通用同步工具CountDownLatch实现线程等待

原文：http://blog.csdn.net/fansunion/article/details/50439484