A linked list + hashtable of pointers to the linked list nodes is the usual way to implement LRU caches. This gives O(1) operations (assuming a decent hash). Advantage of this (being O(1)): you can do a multithreaded version by just locking the whole structure. You don’t have to worry about granular locking etc. Briefly, … Read more
The functools source code is available here: https://github.com/python/cpython/blob/master/Lib/functools.py lru_cache uses the _lru_cache_wrapper decorator (python decorator with arguments pattern) which has a cache dictionary in context in which it saves the return value of the function called (every decorated function will have its own cache dict). The dictionary key is generated with the _make_key function from … Read more
I like lots of these suggestions, but for now I think I’ll stick with LinkedHashMap + Collections.synchronizedMap. If I do revisit this in the future, I’ll probably work on extending ConcurrentHashMap in the same way LinkedHashMap extends HashMap. UPDATE: By request, here’s the gist of my current implementation. private class LruCache<A, B> extends LinkedHashMap<A, B> … Read more