}
  }

  public static class NoOpRunnable implements Runnable {
    public void run() {}
  }

  public static class NoOpCallable implements Callable<Object> {
    @Override
    public Object call() {
      return Boolean.TRUE;
    }
  }

  public static final String TEST_STRING = "a test string";

  public static class StringTask implements Callable<String> {
    public String call() {

 * @since 2.0
 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public final class HashBiMap<K extends @Nullable Object, V extends @Nullable Object>
    extends IteratorBasedAbstractMap<K, V> implements BiMap<K, V>, Serializable {

  /** Returns a new, empty {@code HashBiMap} with the default initial capacity (16). */
  public static <K extends @Nullable Object, V extends @Nullable Object> HashBiMap<K, V> create() {

 * @since 3.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class ForwardingSetMultimap<K extends @Nullable Object, V extends @Nullable Object>
    extends ForwardingMultimap<K, V> implements SetMultimap<K, V> {

  @Override
  protected abstract SetMultimap<K, V> delegate();

  @Override
  public Set<Entry<K, V>> entries() {
    return delegate().entries();
  }

  @Override

 * @since 3.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class ForwardingSortedSetMultimap<
        K extends @Nullable Object, V extends @Nullable Object>
    extends ForwardingSetMultimap<K, V> implements SortedSetMultimap<K, V> {

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

  @Override
  protected abstract SortedSetMultimap<K, V> delegate();

  @Override

 *
 * @author Mike Bostock
 * @since 2.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class ForwardingListIterator<E extends @Nullable Object>
    extends ForwardingIterator<E> implements ListIterator<E> {

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

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

  @Override

 *
 * @author Louis Wasserman
 */
@ElementTypesAreNonnullByDefault
final class UnmodifiableSortedMultiset<E extends @Nullable Object> extends UnmodifiableMultiset<E>
    implements SortedMultiset<E> {
  UnmodifiableSortedMultiset(SortedMultiset<E> delegate) {
    super(delegate);
  }

  @Override
  protected SortedMultiset<E> delegate() {
    return (SortedMultiset<E>) super.delegate();

 *
 * @author Chris Povirk
 * @author Jared Levy
 * @author George van den Driessche
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class TestStringBiMapGenerator implements TestBiMapGenerator<String, String> {

  @Override
  public SampleElements<Entry<String, String>> samples() {
    return new SampleElements<>(
        Helpers.mapEntry("one", "January"),

  @Override
  Object writeReplace() {
    return new SerializedForm<V>(map);
  }

  @GwtIncompatible // serialization
  @J2ktIncompatible
  private static class SerializedForm<V> implements Serializable {
    final ImmutableMap<?, V> map;

    SerializedForm(ImmutableMap<?, V> map) {
      this.map = map;
    }

    Object readResolve() {
      return map.values();
    }

 * our other nullness annotations.
 */
final class Synchronized {
  private Synchronized() {}

  static class SynchronizedObject implements Serializable {
    final Object delegate;
    final Object mutex;

    SynchronizedObject(Object delegate, @CheckForNull Object mutex) {
      this.delegate = checkNotNull(delegate);

    return new ContainsPatternPredicate(new JdkPattern(pattern));
  }

  // End public API, begin private implementation classes.

  // Package private for GWT serialization.
  enum ObjectPredicate implements Predicate<@Nullable Object> {
    /** @see Predicates#alwaysTrue() */
    ALWAYS_TRUE {
      @Override
      public boolean apply(@CheckForNull Object o) {
        return true;
      }

      @Override