*       String}.
 * </ul>
 *
 * This is the same behavior as type-variable usages have to Kotlin and to the Checker Framework.
 * Contrast the method above to:
 *
 * <ul>
 *   <li>methods whose return type is a type variable but which can never return {@code null},
 *       typically because the type forbids nullable type arguments: For example, {@code

import java.util.Map;
import org.jspecify.annotations.Nullable;

/**
 * An object representing the differences between two maps.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@DoNotMock("Use Maps.difference")
@GwtCompatible
public interface MapDifference<K extends @Nullable Object, V extends @Nullable Object> {
  /**

                    @Nonnull Session session,
                    @Nullable RequestTrace trace,
                    @Nullable Path path,
                    @Nullable Source source,
                    boolean allowStubModel,
                    boolean recursive,
                    boolean processPlugins,
                    @Nullable List<RemoteRepository> repositories) {
                super(session, trace);

    TypeVariableInvocationHandler(TypeVariableImpl<?> typeVariableImpl) {
      this.typeVariableImpl = typeVariableImpl;
    }

    @Override
    public @Nullable Object invoke(Object proxy, Method method, @Nullable Object @Nullable [] args)
        throws Throwable {
      String methodName = method.getName();
      Method typeVariableMethod = typeVariableMethods.get(methodName);

import java.util.Map.Entry;
import java.util.Set;
import org.jspecify.annotations.Nullable;

/**
 * Implementation of {@link Multimaps#filterKeys(SetMultimap, Predicate)}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
final class FilteredKeySetMultimap<K extends @Nullable Object, V extends @Nullable Object>
    extends FilteredKeyMultimap<K, V> implements FilteredSetMultimap<K, V> {

      assertTrue(Thread.holdsLock(mutex));
      return delegate.containsRow(rowKey);
    }

    @Override
    public @Nullable V get(Object rowKey, Object columnKey) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.get(rowKey, columnKey);
    }

    @Override
    public @Nullable V put(R rowKey, C columnKey, V value) {
      assertTrue(Thread.holdsLock(mutex));

 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingMultiset<E extends @Nullable Object> extends ForwardingCollection<E>
    implements Multiset<E> {

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

  @Override
  protected abstract Multiset<E> delegate();

  @Override
  public int count(@Nullable Object element) {
    return delegate().count(element);
  }

   *       </ul>
   *   <li>other method calls are dispatched to {@link #handleInvocation}.
   * </ul>
   */
  @Override
  public final @Nullable Object invoke(
      Object proxy, Method method, @Nullable Object @Nullable [] args) throws Throwable {
    if (args == null) {
      args = NO_ARGS;
    }
    if (args.length == 0 && method.getName().equals("hashCode")) {
      return hashCode();
    }

      new IteratorOperation() {
        @Override
        public @Nullable Object execute(Iterator<?> iterator) {
          iterator.remove();
          return null;
        }
      };

  private static final IteratorOperation NEXT_METHOD =
      new IteratorOperation() {
        @Override
        public @Nullable Object execute(Iterator<?> iterator) {
          return iterator.next();
        }

@GwtIncompatible // not worth using in GWT for now
final class CompactLinkedHashMap<K extends @Nullable Object, V extends @Nullable Object>
    extends CompactHashMap<K, V> {
  // TODO(lowasser): implement removeEldestEntry so this can be used as a drop-in replacement

  /** Creates an empty {@code CompactLinkedHashMap} instance. */
  public static <K extends @Nullable Object, V extends @Nullable Object>
      CompactLinkedHashMap<K, V> create() {