A Least-Frequently-Used Map.
This is not a real map in the sense of the Java-Collections-API. This is a slimmed down version of a Least-Frequently-Used map with no unnecessary extra stuff like iterators or other costly but rarely used java.util.Collections features. The cache does not accept null-keys, and any attempt to store null-values will yield an error.
To remove a couple of ugly checks and thus improving performance, this map enforces a minimum size of 3 items.
@author Thomas Morgner