@GwtCompatible
@ElementTypesAreNonnullByDefault
abstract class AbstractListMultimap<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractMapBasedMultimap<K, V> implements ListMultimap<K, V> {
  /**
   * Creates a new multimap that uses the provided map.
   *
   * @param map place to store the mapping from each key to its corresponding values
   */
  protected AbstractListMultimap(Map<K, Collection<V>> map) {
    super(map);
  }

@GwtCompatible
@ElementTypesAreNonnullByDefault
abstract class AbstractListMultimap<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractMapBasedMultimap<K, V> implements ListMultimap<K, V> {
  /**
   * Creates a new multimap that uses the provided map.
   *
   * @param map place to store the mapping from each key to its corresponding values
   */
  protected AbstractListMultimap(Map<K, Collection<V>> map) {
    super(map);
  }

 *
 * <p>TODO(cpovirk): Consider applying this subclass approach to our other types.
 */
@GwtCompatible(emulated = true)
abstract class ArrayListMultimapGwtSerializationDependencies<K, V>
    extends AbstractListMultimap<K, V> {
  ArrayListMultimapGwtSerializationDependencies(Map<K, Collection<V>> map) {
    super(map);
  }
  // TODO(cpovirk): Maybe I should have just one shared superclass for AbstractMultimap itself?

 *
 * <p>TODO(cpovirk): Consider applying this subclass approach to our other types.
 */
@GwtCompatible(emulated = true)
abstract class ArrayListMultimapGwtSerializationDependencies<K, V>
    extends AbstractListMultimap<K, V> {
  ArrayListMultimapGwtSerializationDependencies(Map<K, Collection<V>> map) {
    super(map);
  }
  // TODO(cpovirk): Maybe I should have just one shared superclass for AbstractMultimap itself?

import com.google.common.annotations.GwtCompatible;
import java.util.Collection;
import java.util.Map;

@GwtCompatible(emulated = true)
abstract class ArrayListMultimapGwtSerializationDependencies<K, V>
    extends AbstractListMultimap<K, V> {
  ArrayListMultimapGwtSerializationDependencies(Map<K, Collection<V>> map) {
    super(map);
  }

  K dummyKey;
  V dummyValue;

    return new CustomListMultimap<>(map, factory);
  }

  private static class CustomListMultimap<K extends @Nullable Object, V extends @Nullable Object>
      extends AbstractListMultimap<K, V> {
    transient Supplier<? extends List<V>> factory;

    CustomListMultimap(Map<K, Collection<V>> map, Supplier<? extends List<V>> factory) {
      super(map);
      this.factory = checkNotNull(factory);