Java Future接口与异步计算超时

1，简介与作用

1）代表一个异步计算的结果represents the result of an asynchronous computation.
Future<V>是一个泛型接口，V代表future执行的任务返回值类型。

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2）接口中定义的方法
V get(); Waits if necessary for the computation to complete, and then retrieves its result.等待计算的完成，并取回结果。
V get(long timeout, TimeUnit unit);Waits if necessary for at most the given time for the computation to complete, and then retrieves its result, if available.最大等待timeout时长，然后如果可以获取的话，就取回结果，超时则抛出TimeoutException。
boolean isDone(); Returns true if this task completed.
boolean isCancelled(); Returns true if this task was cancelled before it completed normally.
boolean cancel(boolean mayInterruptIfRunning); Attempts to cancel execution of this task. 参数代表whether this task should be interrupted
3）Future接口常用的实现类
public interface RunnableFuture<V> extends Runnable, Future<V>接口继承了Runnable和Future接口。
public class FutureTask<V> implements RunnableFuture<V>A cancellable asynchronous computation. FutureTask can be used to wrap a Runnable object. A FutureTask can be submitted to an Executor.
4）FutureTask中有私有成员。can be used to wrap a Callable object
private Callable<V> callable; image.png

2，实现代码执行的超时。

1）通过Java线程池ExecutorService类配合Future接口实现，处理的都是比较耗时的操作，超过一定时间没有返回结果，就结束线程。 2）异步计算增加超时时间实例

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