java多线程返回值使用示例(callable与futuretask)

时间:2022-06-03 09:06:27

Callable接口类似于Runnable,从名字就可以看出来了,但是Runnable不会返回结果,并且无法抛出返回结果的异常,而Callable功能更强大一些,被线程执行后,可以返回值,这个返回值可以被Future拿到,也就是说,Future可以拿到异步执行任务的返回值,下面来看一个简单的例子

 

复制代码代码如下:


package com.future.test;

 

import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.FutureTask;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

public class MyTest {

 // 接收在run方法中捕获的异常,然后自定义方法抛出异常
    //private static Throwable exception;
 /**
  * @param args
  */
 public static void main(String[] args) {
  // TODO Auto-generated method stub
  String result = "";
  ExecutorService executor = Executors.newSingleThreadExecutor();  
  FutureTask<String> future =  
         new FutureTask<String>(new Callable<String>() {//使用Callable接口作为构造参数  
           public String call() {  
             //真正的任务在这里执行,这里的返回值类型为String,可以为任意类型
            try {
      Thread.sleep(10000);
     } catch (InterruptedException e) {
      // TODO Auto-generated catch block
      //exception = e;
      //e.printStackTrace();
     }
           return "11111";
         }});  
  executor.execute(future);  
  //在这里可以做别的任何事情  
  try {  
      result = future.get(5000, TimeUnit.MILLISECONDS); //取得结果,同时设置超时执行时间为5秒。同样可以用future.get(),不设置执行超时时间取得结果  
  } catch (InterruptedException e) { 
   //System.out.println("任务已经取消");
   future.cancel(true);  
  } catch (ExecutionException e) {  
   future.cancel(true);  
  } catch (TimeoutException e) {  
   future.cancel(true);  
  } finally {  
      executor.shutdown();  
  }  
  System.out.println("result:"+result);
 }

 /* public void throwException() throws FileNotFoundException, IOException {
         if (exception instanceof FileNotFoundException)
             throw (FileNotFoundException) exception;
         if (exception instanceof IOException)
             throw (IOException) exception;
     }*/


}