Helper for simple bounded LRU maps used for reusing lookup values.
Note that serialization behavior is such that contents are NOT serialized,
on assumption that all use cases are for caching where persistence
does not make sense. The only thing serialized is the cache size of Map.
public LRUMap(int initialEntries, int maxEntries)
super(initialEntries, 0.8f, true);
Ugly hack, to work through the requirement that _value is indeed final,
and that JDK serialization won't call ctor(s) if Serializable is implemented.