which java collections (and maps) can be sorted by last access

i know that the LinkedHashMap provides a constructor, where you can indicate if the map should be sorted by the access order thus effectively开发者_开发问答 providing an LRU implementation. Can you tell me which (and if) other Collections and Maps from the big Collections zoo provide this feature?

I don't think I completely understand the question, but maybe you want to have a look in the LRUMap implementation of the Commons Collections framework.

I don't think any such Collections or Maps exist (but I also heard of that constructor for the first time just now). I have checked Guava, but I don't think they have a solution, either.

But I think it could be easily achieved using the decorator pattern. Write a delegate object that implements the interface you want and delegates all methods to an inner object. Your wrapper also contains a LinkedHashSet / LinkedHashMap (depending on whether you are dealing with a collection or map) that logs data access.

Now your iterator() / entrySet() methods provide a view that's backed first by the LinkedHashSet/Map and then by the rest of the data (or vice-versa if you want to reverse the access order).

I would implement it using wrapper methods like the ones in the Collections class.

E.g.

Map<String,String> map = CollectionUtils.viewMapByAccessOrder(
                             new HashMap<String,String>());
List<String> list = CollectionUtils.viewListByAccessOrder(
                             new ArrayList<String>());

This could actually be functionality that makes sense for a larger audience. I'd consider filing a feature request in the Guava project.