java - java.util.concurrent.DelayQueue俯瞰过期的元素

以下Java代码示例使用Java DelayQueue处理任务。但是，从另一个线程插入任务似乎破坏了(我的)预期行为。

抱歉，代码示例很长，但总而言之:

主线程将5个任务(A-E)添加到具有各种延迟(0ms，10ms，100ms，1000ms，10000ms)的DelayQueue中

启动另一个踏步，它在3000毫秒后将另一个任务添加到DelayQueue中。

主线程轮询DelayQueue并在每个任务到期时报告

8000ms之后，主线程报告了DelayQueue

中剩余的任务

我从代码示例中获得的输出是:

------initial tasks ---------------
task A due in 0ms
task B due in 9ms
task C due in 99ms
task D due in 999ms
task E due in 9999ms
task F due in 99999ms
------processing--------------------
time = 5    task A due in -1ms
time = 14   task B due in 0ms
time = 104  task C due in 0ms
time = 1004 task D due in 0ms
time = 3003 added task Z due in 0ms
------remaining after 15007ms -----------
task F due in 84996ms
task E due in -5003ms
task Z due in -12004ms

我的问题是:为什么在15000ms之后，DelayQueue中仍然有过期的任务(即GetDelay()返回-ve值的地方)？

我检查过的一些东西:

我已经实现了compareTo()来定义任务

的自然顺序

equals()与compareTo()一致

hashCode()已被覆盖

我将最有兴趣学习如何解决此问题。预先感谢您的协助。 (以及迄今为止帮助我的所有那些Stack Overflow答案:)

    package test;

    import java.util.concurrent.DelayQueue;
    import java.util.concurrent.Delayed;
    import java.util.concurrent.TimeUnit;

    public class Test10_DelayQueue {

       private static final TimeUnit delayUnit = TimeUnit.MILLISECONDS;
       private static final TimeUnit ripeUnit = TimeUnit.NANOSECONDS;

       static long startTime;

       static class Task implements Delayed {
          public long ripe;
          public String name;
          public Task(String name, int delay) {
             this.name = name;
             ripe = System.nanoTime() + ripeUnit.convert(delay, delayUnit);
          }

      @Override
      public boolean equals(Object obj) {
         if (obj instanceof Task) {
            return compareTo((Task) obj) == 0;
         }
         return false;
      }

      @Override
      public int hashCode() {
         int hash = 7;
         hash = 67 * hash + (int) (this.ripe ^ (this.ripe >>> 32));
         hash = 67 * hash + (this.name != null ? this.name.hashCode() : 0);
         return hash;
      }

      @Override
      public int compareTo(Delayed delayed) {
         if (delayed instanceof Task) {
            Task that = (Task) delayed;
            return (int) (this.ripe - that.ripe);
         }
         throw new UnsupportedOperationException();
      }

      @Override
      public long getDelay(TimeUnit unit) {
         return unit.convert(ripe - System.nanoTime(), ripeUnit);
      }

      @Override
      public String toString() {
         return "task " + name + " due in " + String.valueOf(getDelay(delayUnit) + "ms");
          }
       }

       static class TaskAdder implements Runnable {

      DelayQueue dq;
      int delay;

      public TaskAdder(DelayQueue dq, int delay) {
         this.dq = dq;
         this.delay = delay;
      }

      @Override
      public void run() {
         try {
            Thread.sleep(delay);

            Task z = new Task("Z", 0);
            dq.add(z);

            Long elapsed = System.currentTimeMillis() - startTime;

            System.out.println("time = " + elapsed + "\tadded " + z);

         } catch (InterruptedException e) {
         }
      }
    }

    public static void main(String[] args) {
      startTime = System.currentTimeMillis();
      DelayQueue<Task> taskQ = new DelayQueue<Task>();

      Thread thread = new Thread(new TaskAdder(taskQ, 3000));
      thread.start();

      taskQ.add(new Task("A", 0));
      taskQ.add(new Task("B", 10));
      taskQ.add(new Task("C", 100));
      taskQ.add(new Task("D", 1000));
      taskQ.add(new Task("E", 10000));
      taskQ.add(new Task("F", 100000));

      System.out.println("------initial tasks ---------------");
      Task[] tasks = taskQ.toArray(new Task[0]);
      for (int i = 0; i < tasks.length; i++) {
         System.out.println(tasks[i]);
      }

      System.out.println("------processing--------------------");
      try {
         Long elapsed = System.currentTimeMillis() - startTime;
         while (elapsed < 15000) {
            Task task = taskQ.poll(1, TimeUnit.SECONDS);
            elapsed = System.currentTimeMillis() - startTime;
            if (task != null) {
               System.out.println("time = " + elapsed + "\t" + task);
            }
         }

         System.out.println("------remaining after " + elapsed + "ms -----------");
         tasks = taskQ.toArray(new Task[0]);
         for (int i = 0; i < tasks.length; i++) {
            System.out.println(tasks[i]);
         }

      } catch (InterruptedException e) {
      }
    }
    }

最佳答案

因为您的comapareTo方法存在很多缺陷。正确的实现如下。一旦您做出如下更改，所有问题都将得到解决。如果或遵守compareTo契约(Contract)，请始终尝试重用compareTo方法

return Long.valueOf(this.ripe).compareTo(that.ripe);