/**
 * An Iterator implementation which draws elements from a queue, removing them from the queue as it
 * iterates. This class is not thread safe.
 */
@GwtCompatible
final class ConsumingQueueIterator<T extends @Nullable Object> extends AbstractIterator<T> {
  private final Queue<T> queue;

  ConsumingQueueIterator(Queue<T> queue) {
    this.queue = checkNotNull(queue);
  }

  @Override
  protected @Nullable T computeNext() {

    result.usingGenerator(generator);
    return result;
  }

  @SuppressWarnings("rawtypes") // class literals
  @Override
  protected List<Class<? extends AbstractTester>> getTesters() {
    List<Class<? extends AbstractTester>> testers = copyToList(super.getTesters());
    testers.add(SetMultimapAsMapTester.class);
    testers.add(SetMultimapEqualsTester.class);
    testers.add(SetMultimapPutTester.class);

    return new CacheLoader<K, V>() {
      @Override
      public V load(K key) throws Exception {
        return loader.load(key);
      }

      @Override
      public Map<K, V> loadAll(Iterable<? extends K> keys) throws Exception {
        Map<K, V> result = new HashMap<>(); // allow nulls
        for (K key : keys) {
          result.put(key, load(key));
        }
        return result;
      }
    };
  }

 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#bimap">{@code BiMap}</a>.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@GwtCompatible
public interface BiMap<K extends @Nullable Object, V extends @Nullable Object> extends Map<K, V> {
  // Modification Operations

  /**
   * {@inheritDoc}
   *
   * @throws IllegalArgumentException if the given value is already bound to a different key in this

 * #elementSet()}. Override those methods for better performance.
 *
 * @author Kevin Bourrillion
 * @author Louis Wasserman
 */
@GwtCompatible
abstract class AbstractMultiset<E extends @Nullable Object> extends AbstractCollection<E>
    implements Multiset<E> {
  // Query Operations

  @Override
  public boolean isEmpty() {
    return entrySet().isEmpty();
  }

  @Override

      }
      return filter(multimap);
    }

    @Override
    public Collection<Integer> createCollection(Iterable<? extends Integer> values) {
      return Sets.newLinkedHashSet(values);
    }
  }

  abstract static class FilteredListMultimapGenerator
      extends TestFilteredMultimapGenerator<ListMultimap<String, Integer>>
      implements TestListMultimapGenerator<String, Integer> {

    @Override

   *
   * @since 11.0 (generics widened in 13.0)
   */
  public static <T> Iterable<T> presentInstances(
      Iterable<? extends Optional<? extends T>> optionals) {
    checkNotNull(optionals);
    return () ->
        new AbstractIterator<T>() {
          private final Iterator<? extends Optional<? extends T>> iterator =
              checkNotNull(optionals.iterator());

          @Override

    setImplementation(Executor.class, Dummies.DummyExecutor.class);
  }

  @SuppressWarnings("unchecked") // it's a subtype map
  private static <T> @Nullable Class<? extends T> getImplementation(Class<T> type) {
    return (Class<? extends T>) implementations.get(type);
  }

  private static final Logger logger = Logger.getLogger(ArbitraryInstances.class.getName());

  /**

   * @since 12.0
   */
  void putAll(Map<? extends K, ? extends V> m);

  /** Discards any cached value for key {@code key}. */
  void invalidate(@CompatibleWith("K") Object key);

  /**
   * Discards any cached values for keys {@code keys}.
   *
   * @since 11.0
   */
  // For discussion of <? extends Object>, see getAllPresent.
  void invalidateAll(Iterable<? extends Object> keys);

    result.usingGenerator(generator);
    return result;
  }

  @SuppressWarnings("rawtypes") // class literals
  @Override
  protected List<Class<? extends AbstractTester>> getTesters() {
    List<Class<? extends AbstractTester>> testers = copyToList(super.getTesters());
    testers.add(SetMultimapAsMapTester.class);
    testers.add(SetMultimapEqualsTester.class);
    testers.add(SetMultimapPutTester.class);