import com.google.common.annotations.J2ktIncompatible;
import java.io.Serializable;
import java.util.Iterator;
import org.jspecify.annotations.Nullable;

@GwtCompatible
final class PairwiseEquivalence<E, T extends @Nullable E> extends Equivalence<Iterable<T>>
    implements Serializable {
  final Equivalence<E> elementEquivalence;

  PairwiseEquivalence(Equivalence<E> elementEquivalence) {

        header);
  }

  private static final class Reference<T> {
    private @Nullable T value;

    @Nullable T get() {
      return value;
    }

    void checkAndSet(@Nullable T expected, @Nullable T newValue) {
      if (value != expected) {
        throw new ConcurrentModificationException();
      }
      value = newValue;
    }

 *
 * @author Jared Levy
 * @since 2.0
 */
@DoNotMock("Use ImmutableMultimap, HashMultimap, or another implementation")
@GwtCompatible
public interface Multimap<K extends @Nullable Object, V extends @Nullable Object> {
  // Query Operations

  /**
   * Returns the number of key-value pairs in this multimap.
   *

    public static Object good(
        String a,
        int b,
        // oneConstantOnly doesn't matter since it's not nullable and can be only 1 value.
        @SuppressWarnings("unused") OneConstantEnum oneConstantOnly,
        // noConstant doesn't matter since it can only be null
        @SuppressWarnings("unused") @Nullable NoConstantEnum noConstant) {
      return new GoodEquals(a, b);
    }

    // instance method ignored

   *
   * <p>The serialized output consists of the number of entries, first key, first value, second key,
   * second value, and so on.
   */
  static <K extends @Nullable Object, V extends @Nullable Object> void writeMap(
      Map<K, V> map, ObjectOutputStream stream) throws IOException {
    stream.writeInt(map.size());
    for (Map.Entry<K, V> entry : map.entrySet()) {

  }

  public void testNullFriendlyTransform() {
    Iterator<@Nullable Integer> input = Arrays.<@Nullable Integer>asList(1, 2, null, 3).iterator();
    Iterator<String> result =
        Iterators.transform(
            input,
            new Function<@Nullable Integer, String>() {
              @Override
              public String apply(@Nullable Integer from) {
                return String.valueOf(from);
              }

import java.io.ObjectOutputStream;
import java.util.HashMap;
import org.jspecify.annotations.Nullable;

/**
 * Multiset implementation backed by a {@link HashMap}.
 *
 * @author Kevin Bourrillion
 * @author Jared Levy
 * @since 2.0
 */
@GwtCompatible
public final class HashMultiset<E extends @Nullable Object> extends AbstractMapBasedMultiset<E> {

   */

  static final class Node<K extends @Nullable Object, V extends @Nullable Object>
      extends SimpleEntry<K, V> {
    @Nullable Node<K, V> next; // the next node (with any key)
    @Weak @Nullable Node<K, V> previous; // the previous node (with any key)
    @Nullable Node<K, V> nextSibling; // the next node with the same key
    @Weak @Nullable Node<K, V> previousSibling; // the previous node with the same key

 */

package com.google.common.util.concurrent;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Preconditions;
import java.util.concurrent.Executor;
import org.jspecify.annotations.Nullable;

/**
 * A {@link ListenableFuture} which forwards all its method calls to another future. Subclasses
 * should override one or more methods to modify the behavior of the backing future as desired per

    SettableFuture<@Nullable Void> settableFuture = SettableFuture.create();
    ArrayList<ListenableFuture<@Nullable Void>> results = new ArrayList<>(50_001);
    results.add(
        serializer.submitAsync(
            new AsyncCallable<@Nullable Void>() {
              @Override
              public ListenableFuture<@Nullable Void> call() {
                return settableFuture;