code: public static <E extends Enum<E>> EnumSet<E> noneOf(Class<E> elementType) {
          Enum<?>[] universe = getUniverse(elementType);
          if (universe == null)
              throw new ClassCastException(elementType + " not an enum");
  
          if (universe.length <= 64)
              return new RegularEnumSet<>(elementType, universe);
          else
              return new JumboEnumSet<>(elementType, universe);
      }
docs: Creates an empty enum set with the specified element type.
  
  @param <E> The class of the elements in the set
  @param elementType the class object of the element type for this enum
  set
  @return An empty enum set of the specified type.
  @throws NullPointerException if <tt>elementType</tt> is null