return new MutableClassToInstanceMap<>(new HashMap<Class<? extends @NonNull B>, B>());
  }

  /**
   * Returns a new {@code MutableClassToInstanceMap} instance backed by a given empty {@code
   * backingMap}. The caller surrenders control of the backing map, and thus should not allow any
   * direct references to it to remain accessible.
   */

                  @Override
                  @SuppressWarnings({"unchecked", "rawtypes"})
                  public Map<Class, Impl> create(Object... elements) {
                    MutableClassToInstanceMap<Impl> map = MutableClassToInstanceMap.create();
                    for (Object object : elements) {
                      Entry<Class, Impl> entry = (Entry<Class, Impl>) object;

 * and a primitive type and its corresponding wrapper type may map to different values.
 *
 * <h3>Implementations</h3>
 *
 * <ul>
 *   <li>{@link ImmutableClassToInstanceMap}
 *   <li>{@link MutableClassToInstanceMap}
 * </ul>
 *
 * <p>To map a generic type to an instance of that type, use {@link
 * com.google.common.reflect.TypeToInstanceMap} instead.
 *
 * <p>See the Guava User Guide article on <a href=