线程如何在完成工作后返回值？

本文介绍了线程如何在完成工作后返回值？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

假设我们有这个简单的例子：

Let's say we have this simple example:

public Example extends Thread{ String temp; public Example(){ } @Override public void run(){ . . . . temp = "a_value"; } public static void main(String[] args) { Example th = new Example(); th.start(); } }

线程如何完成job返回String temp？

How can the Thread after finishing its job return me the String temp?

推荐答案

利用（相对）新的 Callable< T> 而不是Runnable（1.5及更新版本）：

Make use of the (relatively) new Callable<T> instead of Runnable (available in 1.5 and newer versions):

这是一个（简单）示例：

Here is a (simple) example:

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 Main { public static void main(final String[] argv) { final ExecutorService service; final Future<String> task; service = Executors.newFixedThreadPool(1); task = service.submit(new Foo()); try { final String str; // waits the 10 seconds for the Callable.call to finish. str = task.get(); // this raises ExecutionException if thread dies System.out.println(str); } catch(final InterruptedException ex) { ex.printStackTrace(); } catch(final ExecutionException ex) { ex.printStackTrace(); } service.shutdownNow(); } } class Foo implements Callable<String> { public String call() { try { // sleep for 10 seconds Thread.sleep(10 * 1000); } catch(final InterruptedException ex) { ex.printStackTrace(); } return ("Hello, World!"); } }