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

I learned this recently after I accidentally stumbled upon the answer in the Java API. If you ever have a map that uses enums as keys make sure you use EnumMap. It's very simple and much more efficient:

public interface LibraryItem{ ... }

public enum LibraryItemType{ BOOK, CD, VHS, AUDIO; ... }

Map> itemsByType =
    new EnumMap<>(LibraryItemType.class);