ImmutableSet from Guava or Java enum

Question

I read here a nice example about using ImmutableSet from Guava. The example is reported here for the sake of completeness:

public static final ImmutableSet<String> COLOR_NAMES = ImmutableSet.of(
  "red",
  "orange",
  "yellow",
  "green",
  "blue",
  "purple");

class Foo {
  Set<Bar> bars;
  Foo(Set<Bar> bars) {
    this.bars = ImmutableSet.copyOf(bars); // defensive copy!
  }
}

The question is, can I obtain the same result by using a Java enum?

PS: This question added into my mind more chaos!

Answer 1

Can I obtain the same result by using a Java enum?

Yes, you can. Did you try it?

FYI, there's also specialized version of ImmutableSet which holds enum's constants - Sets.immutableEnumSet (internally it uses EnumSet).

Some examples (paraphrasing Wiki examples):

public class Test {

  enum Color {
    RED, ORANGE, YELLOW, GREEN, BLUE, PURPLE;
  }

  static class Baz {
    ImmutableSet<Color> colors;

    Baz(Set<Color> colors) {
      this.colors = Sets.immutableEnumSet(colors); // preserves enum constants 
                                                   // order, not insertion order!
    }
  }

  public static void main(String[] args) {
    ImmutableSet<Color> colorsInInsertionOrder = ImmutableSet.of(
        Color.GREEN, Color.YELLOW, Color.RED);
    System.out.println(colorsInInsertionOrder); // [GREEN, YELLOW, RED]
    Baz baz = new Baz(colorsInInsertionOrder);
    System.out.println(baz.colors); // [RED, YELLOW, GREEN]
  }
}

EDIT (after OP's comment):

Do you want all enum constants in ImmutableSet? Just do:

Sets.immutableEnumSet(EnumSet.allOf(Color.class));