CompletionService获取线程运行结果

朱雀 2023-06-13 04:44 38阅读 0赞

使用CompletionService来实现对任意一个线程运行完后的结果的及时获取。它内部添加了阻塞队列，从而获取feture中的值，然后根据返回值做对应的处理。  
代码示例如下：

package com.dalingjia.thead.future;
    
    import java.util.Random;
    import java.util.concurrent.*;
    
    /**
     * 先执行完的线程先处理的方案
     */
    public class testCallable {
    
        public static void main(String[] args) {
            try {
                completionServiceCount();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        /**
         * 使用CompletionService收集callable结果
         * @throws ExecutionException
         * @throws InterruptedException
         */
        public static void completionServiceCount() throws InterruptedException, ExecutionException {
            ExecutorService executorService = Executors.newCachedThreadPool();
            CompletionService<Integer> completionService = new ExecutorCompletionService<Integer>(executorService);
            int threadNum = 5;
            for (int i = 0; i < threadNum; i++) {
                completionService.submit(getTask(i));
            }
            int sum = 0;
            int temp = 0;
            for (int i = 0; i < threadNum; i++) {
                temp = completionService.take().get();
                sum += temp;
                System.out.print(temp + "\t");
            }
            System.out.println("CompletionService all is : " + sum);
            executorService.shutdown();
        }
    
        public static Callable<Integer> getTask(final int no) {
            final Random rand = new Random();
            Callable<Integer> task = new Callable<Integer>() {
                @Override
                public Integer call() throws Exception {
                    int time = rand.nextInt(100) * 100;
                    System.out.println("thread:" + no + ",sleep time is:" + time);
                    Thread.sleep(time);
                    return no;
                }
            };
            return task;
        }
    }

打印结果：

thread:0,sleep time is:1100
    thread:1,sleep time is:4300
    thread:2,sleep time is:4300
    thread:3,sleep time is:4400
    thread:4,sleep time is:1900
    0	4	2	1	3	CompletionService all is : 10

如果想获取最先返回的一个结果，可以使用System.out.println(completionService.take().get()); 不使用循环。

参考博客：[Java利用CompletionService异步获取多线程执行结果][Java_CompletionService]，[CompletionService异步非阻塞获取并行任务执行结果][CompletionService]

[Java_CompletionService]: https://www.cnblogs.com/clarechen/p/4604189.html
[CompletionService]: https://blog.csdn.net/woshilijiuyi/article/details/78970497