How to implement a most-recently-used cache

Question

What would be the best way to implement a most-recently-used cache of objects?

Here are the requirements and restrictions...

• Objects are stored as key/

Answer 1

Why implement something already implemented? Use Ehcache.

However, if third-party libraries are totally out of the question, I guess you are looking to implement a data structure which looks something like this:

• Basically is a HashMap (extends HashMap if you will)
• Each value in the Map points to an object in a sorted list, based on which is most used.
• Objects recently used are added to the head of the list - O(1)
• Purging least-recently used means truncating the end of the list - O(1)
• Still gives you Map lookups, but still keeps recently-used items first...