使用Future取消超时任务

在某些场景下，获取的资源存在过期时间，超过期望的新鲜时间，再获取到的结果就是无效的，这时可以用Future来取消过期的任务。

public class FutureTimeOutDemo {

    static final ExecutorService executorService = Executors.newFixedThreadPool(5);

    public static void main(String[] args) {
        Future<String> future = null;
        try {
            FutureTimeOutDemo demo = new FutureTimeOutDemo();
            future = demo.getTaskResult();
            //预期获得2000毫秒内返回的结果
            String result = future.get(2000, TimeUnit.MILLISECONDS);
            System.out.println("result is " + result);
        }catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        } catch (TimeoutException e) {
            //取消过期的任务
            future.cancel(true);
            System.out.println("timeout, print the default value: default" );
        }
        executorService.shutdown();
    }

    private Future<String> getTaskResult() throws InterruptedException{
        Callable<String> task = new Callable<String>() {
            @Override
            public String call() throws Exception {
                Thread.sleep(3000);
                return "ok";
            }
        };
         return executorService.submit(task);
    }
}