Java中ExecutorService线程的Callable的future.get()方法堵塞当前线程解决方法

逃离我推掉我的手 2023-09-30 14:45 24阅读 0赞

## 场景 ##

Java中ExecutorService线程池的使用(Runnable和Callable多线程实现)：

[https://blog.csdn.net/BADAO\_LIUMANG\_QIZHI/article/details/126242904][https_blog.csdn.net_BADAO_LIUMANG_QIZHI_article_details_126242904]

在上面学习线程池ExecutorService的使用，实现Callable接口，并获取返回结果时

需要注意future的get()方法会堵塞当前线程的执行。

即当前线程执行结束并获取到结果之后才会继续执行下个线程。

这样就无法实现多线程的效果。

比如：

//        ArrayList<String> resultList = new ArrayList<>();
    //        for (int i = 0; i < 5; i++) {
    //            Future<String> submit = executorService.submit(new CustomTask());
    //            String result = null;
    //            try {
    //                result = submit.get();//get方法能获取到当前线程的执行结果，但是会堵塞当前线程
    //                resultList.add(result);
    //            } catch (InterruptedException e) {
    //                e.printStackTrace();
    //            } catch (ExecutionException e) {
    //                e.printStackTrace();
    //            }
    //        }

执行效果为

![689fe69e1cc14e8487894a64aa8cac1a.gif][]

注：

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## 实现 ##

1、解决方式为创建一个数组存储所有的future,在所有线程循环结束以后再遍历list获取结果。

ArrayList<Future<String>> resultList = new ArrayList<>();
            for (int i = 0; i < 5; i++) {
                Future<String> submit = executorService.submit(new CustomTask());
                resultList.add(submit);
            }
            resultList.forEach(result -> {
                try {
                    System.out.println(result.get());
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (ExecutionException e) {
                    e.printStackTrace();
                }
            });

上面这种执行效果

![47578825d61b40988f401a20e6c5341f.gif][]

2、完整示例代码

package com.ruoyi.demo.Executor;
    
    import com.ruoyi.common.utils.DateUtils;
    
    import java.util.ArrayList;
    import java.util.concurrent.*;
    
    public class CallableDemo {
        public static void main(String[] args) {
            ExecutorService executorService = Executors.newFixedThreadPool(5);
            ArrayList<Future<String>> resultList = new ArrayList<>();
            for (int i = 0; i < 5; i++) {
                Future<String> submit = executorService.submit(new CustomTask());
                resultList.add(submit);
            }
            resultList.forEach(result -> {
                try {
                    System.out.println(result.get());
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (ExecutionException e) {
                    e.printStackTrace();
                }
            });
        }
    }
    
    class CustomTask implements Callable<String> {
    
        @Override
        public String call() throws Exception {
            String threadName = Thread.currentThread().getName();
            System.out.println("线程名:" + threadName + " 开始时间:" + DateUtils.getTime());
            System.out.println("系统需要业务操作1秒");
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            return "threadName = "+threadName +" 结束时间:"+DateUtils.getTime();
        }
    }

[https_blog.csdn.net_BADAO_LIUMANG_QIZHI_article_details_126242904]: https://blog.csdn.net/BADAO_LIUMANG_QIZHI/article/details/126242904
[689fe69e1cc14e8487894a64aa8cac1a.gif]: https://img-blog.csdnimg.cn/689fe69e1cc14e8487894a64aa8cac1a.gif
[CSDN_-C_SpringBoot]: https://blog.csdn.net/badao_liumang_qizhi
[47578825d61b40988f401a20e6c5341f.gif]: https://img-blog.csdnimg.cn/47578825d61b40988f401a20e6c5341f.gif