code: @Override
      public Spliterator<E> spliterator() {
          return Spliterators.spliterator(this, Spliterator.DISTINCT | Spliterator.ORDERED);
      }
docs: Creates a <em><a href="Spliterator.html#binding">late-binding</a></em>
  and <em>fail-fast</em> {@code Spliterator} over the elements in this set.
  
  <p>The {@code Spliterator} reports {@link Spliterator#SIZED},
  {@link Spliterator#DISTINCT}, and {@code ORDERED}.  Implementations
  should document the reporting of additional characteristic values.
  
  @implNote
  The implementation creates a
  <em><a href="Spliterator.html#binding">late-binding</a></em> spliterator
  from the set's {@code Iterator}.  The spliterator inherits the
  <em>fail-fast</em> properties of the set's iterator.
  The created {@code Spliterator} additionally reports
  {@link Spliterator#SUBSIZED}.
  
  @return a {@code Spliterator} over the elements in this set
  @since 1.8