* @return the replacement string, or {@code null} if no escaping was needed
   */
  public static @Nullable String computeReplacement(UnicodeEscaper escaper, int cp) {
    return stringOrNull(escaper.escape(cp));
  }

  private static @Nullable String stringOrNull(char @Nullable [] in) {
    return (in == null) ? null : new String(in);
  }

  public E last() {
    return delegate.last();
  }

  @Override
  public @Nullable E lower(E e) {
    return delegate.lower(checkValid(e));
  }

  @Override
  public @Nullable E pollFirst() {
    return delegate.pollFirst();
  }

  @Override
  public @Nullable E pollLast() {
    return delegate.pollLast();
  }

  @Override
  public boolean remove(Object object) {

    return (Collector) TO_OPTIONAL;
  }

  private static final Object NULL_PLACEHOLDER = new Object();

  private static final Collector<@Nullable Object, ?, @Nullable Object> ONLY_ELEMENT =
      Collector.<@Nullable Object, ToOptionalState, @Nullable Object>of(
          ToOptionalState::new,
          (state, o) -> state.add((o == null) ? NULL_PLACEHOLDER : o),
          ToOptionalState::combine,
          state -> {

  @VisibleForTesting
  static final class ValueEntry<K extends @Nullable Object, V extends @Nullable Object>
      extends SimpleImmutableEntry<K, V> {
    final int smearedValueHash;

    @Nullable ValueEntry<K, V> nextInValueBucket;

    private @Nullable ValueEntry<K, V> predecessorInValueSet;
    private @Nullable ValueEntry<K, V> successorInValueSet;

    private @Nullable ValueEntry<K, V> predecessorInMultimap;

import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * Test cases for a {@link Table} implementation supporting reads and writes.
 *
 * @author Jared Levy
 * @author Louis Wasserman
 */
@GwtCompatible
@NullMarked
public abstract class AbstractTableTest<C extends @Nullable Character>
    extends AbstractTableReadTest<C> {

   */

  public static <V extends @Nullable Object> ListenableFuture<V> catching(
      ListenableFuture<? extends V> input,
      Class<Throwable> exceptionType,
      Function<? super Throwable, ? extends V> fallback,
      Executor executor) {
    return AbstractCatchingFuture.create(input, exceptionType, fallback, executor);
  }

  public static <V extends @Nullable Object> ListenableFuture<V> catchingAsync(

@GwtIncompatible
public abstract class ForwardingNavigableMap<K extends @Nullable Object, V extends @Nullable Object>
    extends ForwardingSortedMap<K, V> implements NavigableMap<K, V> {

  /** Constructor for use by subclasses. */
  protected ForwardingNavigableMap() {}

  @Override
  protected abstract NavigableMap<K, V> delegate();

  @Override
  public @Nullable Entry<K, V> lowerEntry(@ParametricNullness K key) {

@GwtIncompatible
public abstract class ForwardingNavigableMap<K extends @Nullable Object, V extends @Nullable Object>
    extends ForwardingSortedMap<K, V> implements NavigableMap<K, V> {

  /** Constructor for use by subclasses. */
  protected ForwardingNavigableMap() {}

  @Override
  protected abstract NavigableMap<K, V> delegate();

  @Override
  public @Nullable Entry<K, V> lowerEntry(@ParametricNullness K key) {

  protected abstract ListeningExecutorService delegate();

  @Override
  public <T extends @Nullable Object> ListenableFuture<T> submit(Callable<T> task) {
    return delegate().submit(task);
  }

  @Override
  public ListenableFuture<?> submit(Runnable task) {
    return delegate().submit(task);
  }

  @Override
  public <T extends @Nullable Object> ListenableFuture<T> submit(
      Runnable task, @ParametricNullness T result) {

    }
  }

  private static <E extends @Nullable Object> E getElementOrThrow(@Nullable Entry<E> entry) {
    if (entry == null) {
      throw new NoSuchElementException();
    }
    return entry.getElement();
  }

  private static <E extends @Nullable Object> @Nullable E getElementOrNull(
      @Nullable Entry<E> entry) {
    return (entry == null) ? null : entry.getElement();
  }