code: public static <E extends Enum<E>> EnumSet<E> complementOf(EnumSet<E> s) {
          EnumSet<E> result = copyOf(s);
          result.complement();
          return result;
      }
docs: Creates an enum set with the same element type as the specified enum
  set, initially containing all the elements of this type that are
  <i>not</i> contained in the specified set.
  
  @param <E> The class of the elements in the enum set
  @param s the enum set from whose complement to initialize this enum set
  @return The complement of the specified set in this set
  @throws NullPointerException if <tt>s</tt> is null