Returns either the cached Future for the given key or evaluates the given value generating
function producing a
Selects the (potentially non-existing) cache entry with the given key.
Returns a snapshot view of the keys as an iterator, traversing the keys from the least likely to be retained to the most likely.
Clears the cache by removing all entries.
Retrieves the future instance that is currently in the cache for the given key.
Returns the set of keys in the cache, in no particular order Should return in roughly constant time.
Removes the cache item for the given key.
Returns the upper bound for the number of currently cached entries.