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
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);