这一章节我们来讨论一下Callable、Future和FutureTask的用法与关系。
1.关系
(1)Callable是Runnable的封装的异步运算任务
(2)Future用来保存Callable异步运算的结果
(3)FutureTask封装Future的实体类
2.Future
我们在这里详细介绍一下Future,因为它比较复杂,首先看看他的源代码:
public interface Future<V> { boolean cancel(boolean mayInterruptIfRunning); boolean isCancelled(); boolean isDone(); V get() throws InterruptedException, ExecutionException; V get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException; }
它里面包含了几个方法
get:得到结果
get(timeout,unit)计算是否超时得到结果
cancle:取消任务
isDone、isCancle:判断任务状态
3.例子:
Callable和FutureTask
package com.ray.ch17; import java.util.Random; import java.util.concurrent.Callable; import java.util.concurrent.ExecutionException; import java.util.concurrent.FutureTask; public class Test { public static void main(String[] args) throws InterruptedException, ExecutionException { Callable<Integer> callable = new MyCall(); FutureTask<Integer> futureTask = new FutureTask<Integer>(callable); Thread thread = new Thread(futureTask); thread.start(); Thread.sleep(100); if (!futureTask.isDone()) { System.out.println(futureTask.get()); } if (!futureTask.isCancelled()) { futureTask.cancel(true); System.out.println("cancelled"); } } } class MyCall implements Callable<Integer> { @Override public Integer call() throws Exception { System.out.println("doing something..."); Thread.sleep(1000); return new Random().nextInt(50); } }
我们只需要将上面main方法里面的两个if互换就可以得出不同的结果。
Callable和Future
package com.ray.ch17; import java.util.Random; import java.util.concurrent.Callable; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; public class Test { public static void main(String[] args) throws InterruptedException, ExecutionException { ExecutorService executors = Executors.newCachedThreadPool(); Callable<Integer> callable = new MyCall(); Future<Integer> future = executors.submit(callable); System.out.println(future.get()); } } class MyCall implements Callable<Integer> { @Override public Integer call() throws Exception { System.out.println("doing something..."); Thread.sleep(1000); return new Random().nextInt(50); } }
总结:这一章节主要介绍了Callable、Future和FutureTask的用法与关系。
这一章节就到这里,谢谢。
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从头认识java-17.6 Callable、Future和FutureTask
原文:http://blog.csdn.net/raylee2007/article/details/50530062