Class DelayedTask

lowlevel/DelayQueueDemo.java:10–50

import static java.util.concurrent.TimeUnit.*;

class DelayedTask implements Runnable, Delayed {
  private static int counter = 0;
  private final int id = counter++;
  private final int delta;
  private final long trigger;
  protected static List<DelayedTask> sequence =
    new ArrayList<>();
  DelayedTask(int delayInMilliseconds) {
    delta = delayInMilliseconds;
    trigger = System.nanoTime() +
      NANOSECONDS.convert(delta, MILLISECONDS);
    sequence.add(this);
  }
  @Override public long getDelay(TimeUnit unit) {
    return unit.convert(
      trigger - System.nanoTime(), NANOSECONDS);
  }
  @Override public int compareTo(Delayed arg) {
    DelayedTask that = (DelayedTask)arg;
    if(trigger < that.trigger) return -1;
    if(trigger > that.trigger) return 1;
    return 0;
  }
  @Override public void run() {
    System.out.print(this + " ");
  }
  @Override public String toString() {
    return
      String.format("[%d] Task %d", delta, id);
  }
  public String summary() {
    return String.format("(%d:%d)", id, delta);
  }
  public static class EndTask extends DelayedTask {
    EndTask(int delay) { super(delay); }
    @Override public void run() {
      sequence.forEach(dt ->
        System.out.println(dt.summary()));
    }
  }
}

public class DelayQueueDemo {
  public static void