并行执行任务并获取返回结果
CompletionService 执行快的先返回

ExecutorService 例子


public class FutureTest {
	
	private static ExecutorService pool = Executors.newCachedThreadPool();
	private static Random rand = new Random();
	
	public static void main(String[] args) throws Exception {
		System.out.println("FutureTest start "+new Date());	
		int num = 3;
		List<Future<Long>> futures = new ArrayList<Future<Long>>();
		Future<Long> future = null;
		long sleepTime = 500;
		for(int i=0;i<num;i++){
			sleepTime = sleepTime + rand.nextInt(1000);
			// MyCallable 模拟任务 sleep 指定时间返回 
			future = pool.submit(new MyCallable("task"+i,sleepTime));
			futures.add(future);
		}
		for(int i=0;i<num;i++){
			System.out.println(futures.get(i).get());
		}
		pool.shutdown();
	}
}




CompletionService 例子


public class CompleteServiceTest {
	private static ExecutorService pool = Executors.newCachedThreadPool();
	private static Random rand = new Random();
	
	public static void main(String[] args) throws Exception {
		System.out.println("CompleteServiceTest start "+new Date());		
		CompletionService<Long> cs = new ExecutorCompletionService<>(pool);
		int num = 3;	
		long sleepTime = 500;
		for(int i=0;i<num;i++){
			sleepTime = sleepTime + rand.nextInt(1000);
			cs.submit(new MyCallable("task"+i,sleepTime));
		}
		for(int i=0;i<num;i++){
			// 响应快的先返回
			System.out.println(cs.take().get());
		}	
		System.out.println("CompleteService done "+new Date());

		Utils.doSleep(1000);	
		System.out.println("sleep done "+new Date());

		pool.shutdown();
		pool.awaitTermination(10, TimeUnit.SECONDS);
	}
}




完整例子代码

https://gitee.com/dyyx/hellocode/blob/master/src/dyyx/conc/FutureTest.java

https://gitee.com/dyyx/hellocode/blob/master/src/dyyx/conc/CompleteServiceTest.java