Java执行器没有排队任务的能力

本文介绍了Java执行器没有排队任务的能力的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我需要一个Java执行器，如果其他任务正在处理，它会拒绝任务。我想不可能操作工作队列大小。

I need an Java executor that rejects tasks if some other task is processing. I guess it's not possible to get manipulating the working queue size.

有人可能会想知道为什么我需要一个具有这样的特性的执行器。我需要一个能够轻松更改策略并允许非零队列大小的功能。

Someone might wonder why I need an executor with such characteristic in the first place. I need an ability to easily change the policy and allow non-zero queue size.

任何想法？

推荐答案

使用 ThreadPoolExecutor 与 SynchronousQueue （复制自此答案）。

工作：

import java.util.concurrent.RejectedExecutionHandler; import java.util.concurrent.Semaphore; import java.util.concurrent.SynchronousQueue; import java.util.concurrent.ThreadPoolExecutor; import java.util.concurrent.TimeUnit; public class SingleTaskExecutor { public static void main(String[] args) { try { new SingleTaskExecutor().runTest(); } catch (Exception e) { e.printStackTrace(); } } public void runTest() throws Exception { ThreadPoolExecutor tp = new ThreadPoolExecutor(1, 1, 60L, TimeUnit.SECONDS, new SynchronousQueue<Runnable>()); tp.setRejectedExecutionHandler(new RejectedTaskHandler()); final Semaphore oneTaskDone = new Semaphore(0); tp.execute(new Runnable() { @Override public void run() { System.out.println("Sleeping"); try { Thread.sleep(300); } catch (Exception e) { e.printStackTrace();} System.out.println("Done sleeping"); oneTaskDone.release(); } }); tp.execute(new Runnable() { @Override public void run() { System.out.println("Never happends"); } @Override public String toString() { return "Rejected Runnable"; } }); oneTaskDone.acquire(); tp.execute(new Runnable() { @Override public void run() { System.out.println("Running"); } }); tp.shutdown(); tp.awaitTermination(100, TimeUnit.MILLISECONDS); System.out.println("Finished"); } static class RejectedTaskHandler implements RejectedExecutionHandler { @Override public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) { System.out.println("Task rejected: " + r); } } }