JAVA并发编程——executors--从任务中产生返回值

Runnable是执行工作的独立任务，它不返回任何值。如果希望任务在完成时能够返回一个值,那么可以实现Callable接口而不是Runnable接口。

package com.voole.concurrent;

import java.util.ArrayList;
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;

class TaskWithResult implements Callable{

	private int id ;
	public TaskWithResult(int id){
		this.id = id ;
	}
	@Override
	public String call() throws Exception {
		return "result of taskWithResult" + id ;
	}

}
public class CallableDemo {

	public static void main(String[] args){
		ExecutorService exec = Executors.newCachedThreadPool();
		ArrayList> results = new ArrayList>();
		for(int i = 0 ; i < 10 ; i++){
			results.add(exec.submit(new TaskWithResult(i)));
		}
		for(Future fs : results){
			try {
				System.out.println(fs.get());
			} catch (InterruptedException e) {
				e.printStackTrace();
				return ;
			} catch (ExecutionException e) {
				e.printStackTrace();
			}finally{
				exec.shutdown();
			}
		}
	}
}