return new NullRemovalListener<>();
  }

  /** Type-inferring factory method for creating a {@link QueuingRemovalListener}. */
  @GwtIncompatible // ConcurrentLinkedQueue
  static <K, V> QueuingRemovalListener<K, V> queuingRemovalListener() {
    return new QueuingRemovalListener<>();
  }

  /** Type-inferring factory method for creating a {@link CountingRemovalListener}. */

    }
  }

  /**
   * Sorts the array, treating its elements as unsigned 64-bit integers.
   *
   * @since 23.1
   */
  public static void sort(long[] array) {
    checkNotNull(array);
    sort(array, 0, array.length);
  }

  /**
   * Sorts the array between {@code fromIndex} inclusive and {@code toIndex} exclusive, treating its
   * elements as unsigned 64-bit integers.
   *

   * MoreExecutors#listeningDecorator( java.util.concurrent.ExecutorService)}, {@link
   * ListenableFutureTask}, {@link AbstractFuture}, and other utilities over creating plain {@code
   * Future} instances to be upgraded to {@code ListenableFuture} after the fact.
   */
  public static <V extends @Nullable Object> ListenableFuture<V> listenInPoolThread(
      Future<V> future) {

    // requireNonNull accommodates Android's @RecentlyNullable annotation on ThreadLocal.get
    return requireNonNull(DEST_TL.get());
  }

  /**
   * A thread-local destination buffer to keep us from creating new buffers. The starting size is
   * 1024 characters. If we grow past this we don't put it back in the threadlocal, we just keep
   * going and grow as needed.
   */
  private static final ThreadLocal<char[]> DEST_TL =

  /**
   * Returns a builder that creates immutable sorted multisets with an explicit comparator. If the
   * comparator has a more general type than the set being generated, such as creating a {@code
   * SortedMultiset<Integer>} with a {@code Comparator<Number>}, use the {@link Builder} constructor
   * instead.
   *
   * @throws NullPointerException if {@code comparator} is null
   */

 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

/**
 * Static utilities for the eight primitive types and {@code void}, and value types for treating
 * them as unsigned or storing them in immutable arrays.
 *
 * <p>This package is a part of the open-source <a href="https://github.com/google/guava">Guava</a>
 * library.
 *
 * <p>See the Guava User Guide article on <a

        protected char[] escape(char c) {
          // TODO: Fix tests not to call this directly and make it throw an error.
          return null;
        }
      };

  /**
   * Returns a builder for creating simple, fast escapers. A builder instance can be reused and each
   * escaper that is created will be a snapshot of the current builder state. Builders are not
   * thread safe.
   *

   * Builder} constructor.
   */
  public static <B> Builder<B> builder() {
    return new Builder<>();
  }

  /**
   * A builder for creating immutable class-to-instance maps. Example:
   *
   * <pre>{@code
   * static final ImmutableClassToInstanceMap<Handler> HANDLERS =
   *     new ImmutableClassToInstanceMap.Builder<Handler>()

 * unloading an OSGi bundle.
 *
 * <p>{@code com.google.common.base.FinalizableReferenceQueue} loads this class in its own class
 * loader. That way, this class doesn't prevent the main class loader from getting garbage
 * collected, and this class can detect when the main class loader has been garbage collected and
 * stop itself.
 */
// no @ElementTypesAreNonNullByDefault for the reasons discussed above

   * intermediate zero-state. Ways we could deal with this are:
   *
   * - Don't define any of the ConcurrentMap operations. This is the current state of affairs.
   *
   * - Define putIfAbsent and replace as treating zero and absent identically (as currently
   *   implemented below). This is a bit surprising with putIfAbsent, which really becomes
   *   putIfZero.
   *