return spliterator.estimateSize();
    }

    final Comparator<? super E> getComparator() {
      return spliterator.getComparator();
    }

    final long getExactSizeIfKnown() {
      return spliterator.getExactSizeIfKnown();
    }

    final boolean hasCharacteristics(int characteristics) {
      return spliterator.hasCharacteristics(characteristics);
    }
  }

        while (true) {
          Spliterator<T> prefix = spliterator.trySplit();
          if (prefix == null || prefix.getExactSizeIfKnown() == 0) {
            break;
          } else if (spliterator.getExactSizeIfKnown() == 0) {
            spliterator = prefix;
            break;
          }
        }

        // spliterator is known to be nonempty now

    @CanIgnoreReturnValue
    public Builder addAll(LongStream stream) {
      Spliterator.OfLong spliterator = stream.spliterator();
      long size = spliterator.getExactSizeIfKnown();
      if (size > 0) { // known *and* nonempty
        ensureRoomFor(Ints.saturatedCast(size));
      }
      spliterator.forEachRemaining((LongConsumer) this::add);
      return this;
    }

     */
    @CanIgnoreReturnValue
    public Builder addAll(IntStream stream) {
      Spliterator.OfInt spliterator = stream.spliterator();
      long size = spliterator.getExactSizeIfKnown();
      if (size > 0) { // known *and* nonempty
        ensureRoomFor(Ints.saturatedCast(size));
      }
      spliterator.forEachRemaining((IntConsumer) this::add);
      return this;
    }