final class RegularImmutableSet<E> extends ImmutableSet.CachingAsList<E> {
  private static final Object[] EMPTY_ARRAY = new Object[0];
  static final RegularImmutableSet<Object> EMPTY =
      new RegularImmutableSet<>(EMPTY_ARRAY, 0, EMPTY_ARRAY, 0);

  private final transient Object[] elements;
  private final transient int hashCode;
  // the same values as `elements` in hashed positions (plus nulls)

public abstract class TraversalUtil {

    /**
     * Do not instantiate.
     */
    protected TraversalUtil() {
    }

    /** An empty array of {@link Traverser}. */
    protected static final Traverser[] EMPTY_ARRAY = new Traverser[0];

    private static final Logger logger = Logger.getLogger(TraversalUtil.class);

    /** Mapping from URL protocol (as key) to {@link TraverserFactory} (as value). */

    return Spliterators.spliterator(this, SPLITERATOR_CHARACTERISTICS);
  }

  private static final Object[] EMPTY_ARRAY = {};

  @Override
  @J2ktIncompatible // Incompatible return type change. Use inherited (unoptimized) implementation
  public final Object[] toArray() {
    return toArray(EMPTY_ARRAY);
  }

  @CanIgnoreReturnValue
  @Override
  /*
   * This suppression is here for two reasons:
   *