Using DelayQueue with dynamically changing delay times?

Question

Greetings all:
First-time poster, so please be gentle. :-)
I am implementing a cache timer task whose job is to removes idle elements from a cache after x time, and was considering a DelayQueue as potentially more efficient than iterating through the entire cache each time. Important point is that the delay time of elements in the queue will be dynamically changing while they're in the queue, until the point when they become idle, i.e., each time an element's content changes, its expiration time moves further out.
I went looking in the DelayQueue source (and from there to PriorityQueue) as I was interested to see how it implements its sorting mechanism, and it appears to me that it may not handle this properly. Specifically, it appears that the queue is sorted when elements are added or removed but not otherwise, so that you could end up with the head of the queue being an element that has not really expired.
Question: Has anyone used a DelayQueue for this kind of scenario, and if so, did it work as expected?
Thanks,
Brian

Answer 1

If you want this behaviour I suggest you look at
overriding LinkedHashMap as it has a means to
maintain sorted from most recently accessed to last
accessed.
Thus to clear it all you need to do is remove the
oldest elements.Interesting. Currently I'm using a HashMap so changing to a LinkedHashMap would require virtually no changes to existing code. It still won't quite work as-is, though, because access only gets updated on put's and remove's, whereas I would need access updated on any modification to a contained object as well. I'll think about it a bit more - thanks for the suggestion.