Java多线程研究（七）Callable与Future的应用

ExecutorService.submit()会返回一个future.

blic static void main(String[] args) {
		ExecutorService threadPool = Executors.newSingleThreadExecutor();
		Future future = 
		threadPool.submit(
				new Callable<String>() {
					public String call() throws Exception{
						Thread.sleep(2000);
						return "hello";
						};
					}
				);
		
		System.out.println("等待结果");
		try {
			System.out.println("等待结果"+future.get());
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (ExecutionException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}

等待结果
等待结果hello

而如果使用CompletionService.submit方法，会在多个任务运行时，按照完成的先后顺序依次返回，看代码：

ExecutorService threadPool2 = Executors.newFixedThreadPool(10);
		CompletionService<Integer> completionService = new ExecutorCompletionService<Integer>(threadPool2);
		for(int i=0;i<10;++i){
			final int seq = i;
			
			completionService.submit(new Callable<Integer>() {
	
				@Override
				public Integer call() throws Exception {
					Thread.sleep(new Random().nextInt(5000));
					return seq;
				}
				
			});
			}
		for(int i=0;i<10;++i){
			try {
				System.out.println(completionService.take().get());
			} catch (InterruptedException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (ExecutionException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}

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Java多线程研究（七）Callable与Future的应用

原文：http://blog.csdn.net/howlaa/article/details/18459925