【并发编程】- ExecutorCompletionService使用take()方法获取最先执行完的任务

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ExecutorCompletionService使用take()方法获取最先执行完的任务

运行类执行代码如下：

@Slf4j
public class CompletionServiceTakeRun {
    public static void main(String[] args) {
        ExecutorService executorService = Executors.newCachedThreadPool();
        ExecutorCompletionService completionService = new ExecutorCompletionService(executorService);
        for (int i = 0; i < 10 ; i++) {
            completionService.submit(new Callable<String>() {
                @Override
                public String call() throws Exception {
                    long sleepTime =(int)((Math.random()) * 1000);
                    log.info("线程名：{}，休眠时间：{}",Thread.currentThread().getName(),sleepTime);
                    Thread.sleep(sleepTime);
                    return "休眠时间: "+sleepTime+"线程名: "+Thread.currentThread().getName();
                }
            });
        }
        for (int i = 0; i < 10 ; i++) {
            try {
                log.info("获取线程返回值：{}",completionService.take().get());
            } catch (InterruptedException e) {
                e.printStackTrace();
            } catch (ExecutionException e) {
                e.printStackTrace();
            }
        }
    }
}

运行结果如下：

[pool-1-thread-8] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 线程名：pool-1-thread-8，休眠时间：180

[pool-1-thread-4] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 线程名：pool-1-thread-4，休眠时间：562

[pool-1-thread-6] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 线程名：pool-1-thread-6，休眠时间：905

[pool-1-thread-7] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 线程名：pool-1-thread-7，休眠时间：454

[pool-1-thread-9] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 线程名：pool-1-thread-9，休眠时间：921

[pool-1-thread-3] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 线程名：pool-1-thread-3，休眠时间：411

[pool-1-thread-10] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 线程名：pool-1-thread-10，休眠时间：259

[pool-1-thread-2] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 线程名：pool-1-thread-2，休眠时间：166

[pool-1-thread-5] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 线程名：pool-1-thread-5，休眠时间：188

[pool-1-thread-1] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 线程名：pool-1-thread-1，休眠时间：829

[main] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 获取线程返回值：休眠时间: 166线程名: pool-1-thread-2

[main] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 获取线程返回值：休眠时间: 180线程名: pool-1-thread-8

[main] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 获取线程返回值：休眠时间: 188线程名: pool-1-thread-5

[main] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 获取线程返回值：休眠时间: 259线程名: pool-1-thread-10

[main] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 获取线程返回值：休眠时间: 411线程名: pool-1-thread-3

[main] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 获取线程返回值：休眠时间: 454线程名: pool-1-thread-7

[main] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 获取线程返回值：休眠时间: 562线程名: pool-1-thread-4

[main] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 获取线程返回值：休眠时间: 829线程名: pool-1-thread-1

[main] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 获取线程返回值：休眠时间: 905线程名: pool-1-thread-6

[main] INFO com.ozx.concurrentprogram.executor.controller.CompletionServiceTakeRun - 获取线程返回值：休眠时间: 921线程名: pool-1-thread-9

从运行结果看出ExecutorCompletionService的take()方法是按任务执行的速度，从执行时间短到执行时间长的顺序获取Future对象，所以输出休眠时间从小到大排列。