@GwtCompatible(serializable = true)
  public static <E extends Enum<E>> ImmutableSet<E> immutableEnumSet(
      E anElement, E... otherElements) {
    return ImmutableEnumSet.asImmutable(EnumSet.of(anElement, otherElements));
  }
@GwtCompatible(serializable = true)
  public static <E extends Enum<E>> ImmutableSet<E> immutableEnumSet(
      E anElement, E... otherElements) {
    return ImmutableEnumSet.asImmutable(EnumSet.of(anElement, otherElements));
  }
@ GwtCompatible ( serializable = true ) public static < E extends Enum < E > > ImmutableSet < E > immutableEnumSet ( E anElement , E ... otherElements ) { return ImmutableEnumSet . asImmutable ( EnumSet . of ( anElement , otherElements ) ) ; }
http://code.google.com/p/google-web-toolkit/issues/detail?id=3028
http : // code . google . com / p / google - web - toolkit / issues / detail?id = 3028