CallableAndFuture 返回线程执行完后的结果_future callable 等待全部执行完成-优快云博客

本文链接：https://blog.youkuaiyun.com/qq_39716220/article/details/84894691

本文深入探讨了Java中Callable接口和Future类的使用方法，通过示例展示了如何利用Callable创建有返回值的任务，以及如何使用Future获取任务执行结果。此外，还介绍了如何结合ExecutorService和CompletionService来管理和获取一组任务的执行结果。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

package cn.itcast.heima2;

import java.util.Random;
import java.util.concurrent.Callable;
import java.util.concurrent.CompletionService;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorCompletionService;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;

//返回线程执行完后的结果
public class CallableAndFuture {

   /**
   * @param args
   */
   public static void main(String[] args) {
       ExecutorService threadPool = Executors.newSingleThreadExecutor();
       //Future<T> 返回的结果
       Future<String> future =
           threadPool.submit(
               new Callable<String>() { //需要执行的任务
                   public String call() throws Exception {
                       Thread.sleep(2000);
                       return "hello";
                   };
               }
       );
       System.out.println("等待结果");
       try {
           System.out.println("拿到结果：" + future.get()); //拿到返回结果需要等待
       } catch (InterruptedException e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
       } catch (Exception e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
       }

       ExecutorService threadPool2 = Executors.newFixedThreadPool(10);
       //提交一组任务
       CompletionService<Integer> completionService = new ExecutorCompletionService<Integer>(threadPool2);
       for(int i=1;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 {
               //获取每个任务的返回值
               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();
           }
       }
   }