I recently learnt about the benefits of EnumMap in Java and would like to replace the existing
Guava contributor here.
Guava doesn't currently have an
ImmutableEnumMap variant, but if it did, it would probably just be a wrapper around an
EnumMap. (That said, slightly better immutable implementations are possible.)
EnumMap will perform better than the basic
ImmutableMap, in any event; it's difficult or impossible to beat.
(I'll file an issue to investigate adding an
ImmutableMap variant for enum key types, though.)
Update: Guava 14 adds