multiset.add("a");
    assertThrows(UnsupportedOperationException.class, () -> multiset.remove("a"));
    assertTrue(multiset.contains("a"));
  }

  private static class NoRemoveMultiset<E extends @Nullable Object> extends AbstractMultiset<E>
      implements Serializable {
    final Map<E, Integer> backingMap = new HashMap<>();

    @Override
    public int size() {
      return Multisets.linearTimeSizeImpl(this);

 * methods that they depend on are thread-safe.
 *
 * @author Mike Bostock
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
public abstract class ForwardingMapEntry<K extends @Nullable Object, V extends @Nullable Object>
    extends ForwardingObject implements Map.Entry<K, V> {
  // TODO(lowasser): identify places where thread safety is actually lost

  /** Constructor for use by subclasses. */

@GwtCompatible
@NullMarked
public abstract class IteratorTester<E extends @Nullable Object>
    extends AbstractIteratorTester<E, Iterator<E>> {
  /**
   * Creates an IteratorTester.
   *
   * @param steps how many operations to test for each tested pair of iterators
   * @param features the features supported by the iterator
   */
  protected IteratorTester(
      int steps,
      Iterable<? extends IteratorFeature> features,

 * not its subclasses) can be reused when copied from one ImmutableMap to another.
 *
 * @author Louis Wasserman
 */
@GwtIncompatible // unnecessary
class ImmutableMapEntry<K, V> extends SimpleImmutableEntry<K, V> {
  /**
   * Creates an {@code ImmutableMapEntry} array to hold parameterized entries. The result must never
   * be upcast back to ImmutableMapEntry[] (or Object[], etc.), or allowed to escape the class.

 * to prioritize memory over CPU.
 *
 * @author Louis Wasserman
 * @author Jon Noack
 */
@GwtIncompatible // not worth using in GWT for now
class CompactHashMap<K extends @Nullable Object, V extends @Nullable Object>
    extends AbstractMap<K, V> implements Serializable {
  /*
   * TODO: Make this a drop-in replacement for j.u. versions, actually drop them in, and test the

        }
        return indexName;
    }

    @Override
    protected <RESULT extends Role> RESULT createEntity(final Map<String, Object> source, final Class<? extends RESULT> entityType) {
        try {
            final RESULT result = entityType.newInstance();
            result.setName(DfTypeUtil.toString(source.get("name")));

  @J2ktIncompatible
  @GwtIncompatible // PriorityBlockingQueue
  public static <E extends Comparable> PriorityBlockingQueue<E> newPriorityBlockingQueue(
      Iterable<? extends E> elements) {
    if (elements instanceof Collection) {
      return new PriorityBlockingQueue<>((Collection<? extends E>) elements);
    }
    PriorityBlockingQueue<E> queue = new PriorityBlockingQueue<>();

    public interface FilteredCall<CQ extends EsAbstractConditionQuery, CF extends EsAbstractConditionQuery> {

        void callback(CQ query, CF filter);
    }

    @FunctionalInterface
    public interface OperatorCall<CQ extends EsAbstractConditionQuery> {

        void callback(CQ query);
    }

    @FunctionalInterface
    public interface ScoreFunctionCall<CC extends ScoreFunctionCreator<?>> {

  private static final ConcurrentMap<
          Class<? extends Enum<?>>, Map<? extends Enum<?>, LockGraphNode>>
      lockGraphNodesPerType = new MapMaker().weakKeys().makeMap();

  /** Creates a {@code CycleDetectingLockFactory.WithExplicitOrdering<E>}. */
  public static <E extends Enum<E>> WithExplicitOrdering<E> newInstanceWithExplicitOrdering(
      Class<E> enumClass, Policy policy) {

 * An abstract class that serves as a builder for creating and executing requests.
 *
 * @param <Req> the type of the request
 * @param <Res> the type of the response
 */
public abstract class RequestBuilder<Req extends Request<Res>, Res extends Response> {
    /** The OpenSearch client. */
    protected Client client;
    /** The request being built. */
    protected Req request;

    /**
     * Constructor for RequestBuilder.