Arrays.spliterator(new String[] {"abc", "", "de", "f", "g", ""}),
                    (String str) -> charactersOf(str).spliterator(),
                    Spliterator.SIZED | Spliterator.DISTINCT | Spliterator.NONNULL,
                    7))
        .expect('a', 'b', 'c', 'd', 'e', 'f', 'g');
  }

  public void testFlatMap_nullStream() {
    SpliteratorTester.of(
            () ->
                CollectSpliterators.flatMap(

  }

  /**
   * Returns a predicate that evaluates to {@code true} if the object reference being tested is not
   * null.
   *
   * <p><b>Discouraged:</b> Prefer using either {@code x -> x != null} or {@code Objects::nonNull},
   * but note that lambdas and method references do not have human-readable {@link #toString()}
   * representations and are not serializable.
   */
  public static <T extends @Nullable Object> Predicate<T> notNull() {

  }

  /**
   * Returns a predicate that evaluates to {@code true} if the object reference being tested is not
   * null.
   *
   * <p><b>Discouraged:</b> Prefer using either {@code x -> x != null} or {@code Objects::nonNull},
   * but note that lambdas and method references do not have human-readable {@link #toString()}
   * representations and are not serializable.
   */
  public static <T extends @Nullable Object> Predicate<T> notNull() {

import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeSet;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicInteger;
import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

/**
 * A comparator, with additional methods to support common operations. This is an "enriched" version

import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeSet;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicInteger;
import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

/**
 * A comparator, with additional methods to support common operations. This is an "enriched" version

     */
    public ImmutableSet<@NonNull E> immutableCopy() {
      // Not using ImmutableSet.copyOf() to avoid iterating thrice (isEmpty, size, iterator).
      int maxSize = maxSize();
      if (maxSize == 0) {
        return ImmutableSet.of();
      }
      ImmutableSet.Builder<@NonNull E> builder = ImmutableSet.builderWithExpectedSize(maxSize);
      for (E element : this) {

  }

  @GwtIncompatible
  @J2ktIncompatible
  public void testEntrySetSpliteratorCharacteristics() {
    int expectedCharacteristics =
        Spliterator.DISTINCT | Spliterator.ORDERED | Spliterator.NONNULL | Spliterator.IMMUTABLE;
    Spliterator<Entry<AnEnum, String>> spliterator =
        immutableEnumMap(ImmutableMap.of(AnEnum.A, "a", AnEnum.B, "b")).entrySet().spliterator();

     */
    public ImmutableSet<@NonNull E> immutableCopy() {
      // Not using ImmutableSet.copyOf() to avoid iterating thrice (isEmpty, size, iterator).
      int maxSize = maxSize();
      if (maxSize == 0) {
        return ImmutableSet.of();
      }
      ImmutableSet.Builder<@NonNull E> builder = ImmutableSet.builderWithExpectedSize(maxSize);
      for (E element : this) {

  @CollectionSize.Require(absent = ZERO)
  public void testSpliteratorNullable() {
    initCollectionWithNullElement();
    assertFalse(collection.spliterator().hasCharacteristics(Spliterator.NONNULL));
  }

  @CollectionFeature.Require(SUPPORTS_ADD)
  public void testSpliteratorNotImmutable_collectionAllowsAdd() {
    // If add is supported, verify that IMMUTABLE is not reported.

  @Override
  @GwtIncompatible // Spliterator
  public Spliterator<V> spliterator() {
    return CollectSpliterators.map(
        map.entrySet().spliterator(),
        Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL,
        Entry::getValue);
  }

  @Override
  public boolean contains(@Nullable Object object) {
    return object != null && Iterators.contains(iterator(), object);
  }

  @Override