abstract boolean tryAdvance(Consumer<? super E> action);

    abstract @Nullable GeneralSpliterator<E> trySplit();

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

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

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

      }

      @Override
      public long estimateSize() {
        return fromSpliterator.estimateSize();
      }

      @Override
      public int characteristics() {
        return fromSpliterator.characteristics()
            & ~(Spliterator.DISTINCT | Spliterator.NONNULL | Spliterator.SORTED);
      }
    };
  }

  /** Returns a {@code Spliterator} filtered by the specified predicate. */

  public final CollectorTester<T, A, R> expectCollects(R expectedResult, T... inputs) {
    List<T> list = Arrays.asList(inputs);
    doExpectCollects(expectedResult, list);
    if (collector.characteristics().contains(Collector.Characteristics.UNORDERED)) {
      Collections.reverse(list);
      doExpectCollects(expectedResult, list);
    }
    return this;
  }

    return Collector.of(
        EnumSetAccumulator::new,
        EnumSetAccumulator::add,
        EnumSetAccumulator::combine,
        EnumSetAccumulator::toImmutableSet,
        Collector.Characteristics.UNORDERED);
  }

  @IgnoreJRERequirement // see enclosing class (whose annotation Animal Sniffer ignores here...)
  private static final class EnumSetAccumulator<E extends Enum<E>> {

@SuppressWarnings("serial") // we're overriding default serialization
@ElementTypesAreNonnullByDefault
public abstract class ImmutableCollection<E> extends AbstractCollection<E> implements Serializable {
  static final int SPLITERATOR_CHARACTERISTICS =
      Spliterator.IMMUTABLE | Spliterator.NONNULL | Spliterator.ORDERED;

  ImmutableCollection() {}

  public abstract UnmodifiableIterator<E> iterator();

  public boolean contains(@Nullable Object object) {

    return Collector.of(
        EnumSetAccumulator::new,
        EnumSetAccumulator::add,
        EnumSetAccumulator::combine,
        EnumSetAccumulator::toImmutableSet,
        Collector.Characteristics.UNORDERED);
  }

  private static final class EnumSetAccumulator<E extends Enum<E>> {
    @SuppressWarnings({"rawtypes", "unchecked"})

      Collector.of(
          ToOptionalState::new,
          ToOptionalState::add,
          ToOptionalState::combine,
          ToOptionalState::getOptional,
          Collector.Characteristics.UNORDERED);

  /**
   * A collector that converts a stream of zero or one elements to an {@code Optional}.
   *
   * @throws IllegalArgumentException if the stream consists of two or more elements.

      }
    }
  }

  /**
   * Test for 2-bit characteristics. A characteristic is a delta in the input which is repeated in
   * the output. For example, if f() is a block cipher and c is a characteristic, then f(x^c) =
   * f(x)^c with greater than expected probability. The test for funneling is merely a test for
   * 1-bit characteristics.
   *

  @Override
  public UnmodifiableIterator<E> iterator() {
    return asList().iterator();
  }

  @Override
  public Spliterator<E> spliterator() {
    return CollectSpliterators.indexed(size(), SPLITERATOR_CHARACTERISTICS, this::get);
  }

  @Override
  public void forEach(Consumer<? super E> consumer) {
    checkNotNull(consumer);
    int n = size();
    for (int i = 0; i < n; i++) {
      consumer.accept(get(i));
    }

  }

  @Override
  public Spliterator<E> spliterator() {
    return CollectSpliterators.indexed(
        size(),
        ImmutableList.SPLITERATOR_CHARACTERISTICS | Spliterator.SORTED | Spliterator.DISTINCT,
        delegateList()::get,
        comparator());
  }

  // redeclare to help optimizers with b/310253115
  @SuppressWarnings("RedundantOverride")
  @Override