code: public static Spliterator.OfDouble spliteratorUnknownSize(PrimitiveIterator.OfDouble iterator,
                                                                int characteristics) {
          return new DoubleIteratorSpliterator(Objects.requireNonNull(iterator), characteristics);
      }
docs: Creates a {@code Spliterator.OfDouble} using a given
  {@code DoubleStream.DoubleIterator} as the source of elements, with no
  initial size estimate.
  
  <p>The spliterator is not
  <em><a href="Spliterator.html#binding">late-binding</a></em>, inherits
  the <em>fail-fast</em> properties of the iterator, and implements
  {@code trySplit} to permit limited parallelism.
  
  <p>Traversal of elements should be accomplished through the spliterator.
  The behaviour of splitting and traversal is undefined if the iterator is
  operated on after the spliterator is returned.
  
  @param iterator The iterator for the source
  @param characteristics Characteristics of this spliterator's source
  or elements ({@code SIZED} and {@code SUBSIZED}, if supplied, are
  ignored and are not reported.)
  @return A spliterator from an iterator
  @throws NullPointerException if the given iterator is {@code null}