Combining Java EnumSets

Question

If I have an Enum, I can create an EnumSet using the handy EnumSet class

enum Suit { CLUBS, DIAMONDS, HEARTS, SPADES }
EnumSet<Suit> reds = EnumSet.of(Suit.HEARTS, Suit.DIAMONDS);
EnumSet<Suit> blacks = EnumSet.of(Suit.CLUBS, Suit.SPADES);

Give two EnumSets, how can I create a new EnumSet which contains the union of both of those sets?

EnumSet<Suit> redAndBlack = ?

Answer 1

An EnumSet is also a collection, so you can use many of the Collection API calls as well, such as addAll.

EnumSet<Suit> redAndBlack = EnumSet.copyOf(reds);
redAndBlack.addAll(blacks);

Answer 2

Here's the answer extracted into a generic that you can use with any two EnumSet<T>'s to merge them.

private <T extends Enum<T>> EnumSet<T> mergeEnumSet(EnumSet<T> a, EnumSet<T> b) {
    final EnumSet<T> union = EnumSet.copyOf(a);
    union.addAll(b);
    return union;
}

Answer 3

In this case, you could also use

EnumSet<Suit> redAndBlack = EnumSet.allOf(Suit.class)