How to efficiently use Enum objects as keys in the Map data structure?

Question

Is there a more efficient and specialized implementation of a Map collection where Enum objects can serve as keys?

Answer 1

Yes. EnumMap is precisely that; an efficient implementation of the Map interface, in which the key type must be an enum:

From the API documentation:

Class EnumMap,V>

A specialized Map implementation for use with enum type keys. All of the keys in an enum map must come from a single enum type that is specified, explicitly or implicitly, when the map is created. Enum maps are represented internally as arrays. This representation is extremely compact and efficient.

Example usage:

Map map = new EnumMap(MyEnum.class);