Java多线程Future的使用

先直接上代码如下：

一、需要实现Callable接口（可以使用泛型）

package com.innotek.spms.service.finance;

import com.innotek.common.util.SpringContextUtil;
import com.innotek.spms.entity.busi.Collector;
import com.innotek.spms.entity.busi.Payment;
import com.innotek.spms.entity.fanc.PaymentCard;
import com.innotek.spms.entity.swap.OwefeeRecord;
import com.innotek.spms.entity.swap.RepayRecord;
import com.innotek.spms.entity.tran.PayOrder;
import com.innotek.spms.service.PayBackService;
import org.springframework.beans.factory.annotation.Autowired;

import java.util.concurrent.Callable;

public class RepayTask implements Callable {

    private PayOrder payOrder;
    private Collector collector;
    private Payment payment;
    private String payAccount;
    private String cityCode;
    private OwefeeRecord owefeeRecord;
    private RepayRecord tempEntity;
    private long oweFee;
    private long paymentId;
    private PaymentCard card;

    public RepayTask(PayOrder payOrder, Collector collector, Payment payment,
                     String payAccount, String cityCode, OwefeeRecord owefeeRecord, RepayRecord tempEntity,
                     long oweFee, long paymentId, PaymentCard card) {

        this.payOrder=payOrder;
        this.collector=collector;
        this.payment=payment;
        this.payAccount=payAccount;
        this.cityCode=cityCode;
        this.owefeeRecord=owefeeRecord;
        this.tempEntity=tempEntity;
        this.oweFee=oweFee;
        this.paymentId=paymentId;
        this.card=card;
    }


    @Override
    public Long call() throws Exception {
        PayBackService payBackService=(PayBackService) SpringContextUtil.getBean("payBackService");

        return    payBackService.eliminateRecordImpl(payOrder, collector, payment,
                payAccount, cityCode, owefeeRecord, tempEntity, oweFee,
                paymentId, card);


    }
}

二、创建线程池使用：

// 线程执行补缴接口
ExecutorService executor= Executors.newCachedThreadPool();
List taskList=new ArrayList();
RepayTask task=new RepayTask(payOrder, collector, payment,
    payAccount, cityCode, owefeeRecord, tempEntity, oweFee,
    paymentIdFianl, card);
taskList.add(task);
List>resultList=null;
try {
	//执行全部的线程
    resultList=executor.invokeAll(taskList);
    if(CollectionUtils.isNotEmpty(resultList)){
    	for (int i=0; i future=resultList.get(i);
    		sum+=  future.get();
    	}
    }
} catch (Exception e) {
    e.printStackTrace();
}

三、其他详解如下：

并发编程时，一般使用runnable，然后扔给线程池完事，这种情况下不需要线程的结果。 
所以run的返回值是void类型。 

如果是一个多线程协作程序，比如菲波拉切数列，1，1，2，3，5，8...使用多线程来计算。 
但后者需要前者的结果，就需要用callable接口了。 
callable用法和runnable一样，只不过调用的是call方法，该方法有一个泛型返回值类型，你可以任意指定。 

线程是属于异步计算模型，所以你不可能直接从别的线程中得到函数返回值。 
 这时候，Future就出场了。Futrue可以监视目标线程调用call的情况，当你调用Future的get()方法以获得结果时，当前线程就开始阻塞，直接call方法结束返回结果。 

下面三段简单的代码可以很简明的揭示这个意思： 
 
runnable接口实现的没有返回值的并发编程。 
 
callable实现的存在返回值的并发编程。（call的返回值String受泛型的影响） 
 
同样是callable，使用Future获取返回值。

package demo.future;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.*;

/**
 * 试验 Java 的 Future 用法
 */
public class FutureTest {

    public static class Task implements Callable<String> {
        @Override
        public String call() throws Exception {
            String tid = String.valueOf(Thread.currentThread().getId());
            System.out.printf("Thread#%s : in call\n", tid);
            return tid;
        }
    }

    public static void main(String[] args) throws InterruptedException, ExecutionException {
        List> results = new ArrayList>();
        ExecutorService es = Executors.newCachedThreadPool();
        for(int i=0; i<100;i++)
            results.add(es.submit(new Task()));

        for(Future res : results)
            System.out.println(res.get());
    }

}