extends FlatMapSpliteratorOfPrimitive<
          InElementT, Double, DoubleConsumer, Spliterator.OfDouble>
      implements Spliterator.OfDouble {
    FlatMapSpliteratorOfDouble(
        Spliterator.@Nullable OfDouble prefix,
        Spliterator<InElementT> from,
        Function<? super InElementT, Spliterator.@Nullable OfDouble> function,
        int characteristics,
        long estimatedSize) {
      super(

      extends FlatMapSpliteratorOfPrimitive<
          InElementT, Double, DoubleConsumer, Spliterator.OfDouble>
      implements Spliterator.OfDouble {
    FlatMapSpliteratorOfDouble(
        Spliterator.@Nullable OfDouble prefix,
        Spliterator<InElementT> from,
        Function<? super InElementT, Spliterator.@Nullable OfDouble> function,
        int characteristics,
        long estimatedSize) {
      super(

                    Spliterator.SIZED | Spliterator.DISTINCT | Spliterator.NONNULL,
                    4))
        .expect(1L, 1L, 2L, 3L);
  }

  public void testFlatMapToDouble_nullStream() {
    SpliteratorTester.ofDouble(
            () ->
                CollectSpliterators.flatMapToDouble(
                    Arrays.spliterator(new Double[] {1.0, 0.0, 1.0, 2.0, 3.0}),

    long estimatedSize = 0L;
    ImmutableList.Builder<Spliterator.OfDouble> splitrsBuilder =
        new ImmutableList.Builder<>(streams.length);
    for (DoubleStream stream : streams) {
      isParallel |= stream.isParallel();
      Spliterator.OfDouble splitr = stream.spliterator();
      splitrsBuilder.add(splitr);
      characteristics &= splitr.characteristics();

                    Spliterator.SIZED | Spliterator.DISTINCT | Spliterator.NONNULL,
                    4))
        .expect(1L, 1L, 2L, 3L);
  }

  public void testFlatMapToDouble_nullStream() {
    SpliteratorTester.ofDouble(
            () ->
                CollectSpliterators.flatMapToDouble(
                    Arrays.spliterator(new Double[] {1.0, 0.0, 1.0, 2.0, 3.0}),

     */
    @IgnoreJRERequirement // Users will use this only if they're already using streams.
    @CanIgnoreReturnValue
    public Builder addAll(DoubleStream stream) {
      Spliterator.OfDouble spliterator = stream.spliterator();
      long size = spliterator.getExactSizeIfKnown();
      if (size > 0) { // known *and* nonempty
        ensureRoomFor(Ints.saturatedCast(size));
      }

        .containsExactly(0.0, 1.0, 3.0, 6.0, 10.0, 15.0, 21.0)
        .inOrder();
  }

  public void testAsListIterator() {
    PrimitiveIterator.OfDouble doubleIterator =
        (PrimitiveIterator.OfDouble) ImmutableDoubleArray.of(1.0, 2.0, 3.0).asList().iterator();
    assertThat(doubleIterator.nextDouble()).isEqualTo(1.0);
    assertThat(doubleIterator.nextDouble()).isEqualTo(2.0);

    /*
     * This is an override that is not directly visible to callers, so NewApi will catch calls to
     * Collection.spliterator() where necessary.
     */
    @IgnoreJRERequirement
    public Spliterator.OfDouble spliterator() {
      return Spliterators.spliterator(array, start, end, 0);
    }

    @Override
    public boolean contains(@Nullable Object target) {
      // Overridden to prevent a ton of boxing