}

    @Override
    public @Nullable Entry<K, V> lowerEntry(K key) {
      return standardLowerEntry(key);
    }

    @Override
    public @Nullable K lowerKey(K key) {
      return standardLowerKey(key);
    }

    @Override
    public @Nullable Entry<K, V> floorEntry(K key) {
      return standardFloorEntry(key);
    }

    @Override
    public @Nullable K floorKey(K key) {

    }

    @Override
    public @Nullable Entry<K, V> lowerEntry(K key) {
      return standardLowerEntry(key);
    }

    @Override
    public @Nullable K lowerKey(K key) {
      return standardLowerKey(key);
    }

    @Override
    public @Nullable Entry<K, V> floorEntry(K key) {
      return standardFloorEntry(key);
    }

    @Override
    public @Nullable K floorKey(K key) {

   * {@link #lowerEntry}, you may wish to override {@code lowerKey} to forward to this
   * implementation.
   */
  protected @Nullable K standardLowerKey(@ParametricNullness K key) {
    return keyOrNull(lowerEntry(key));
  }

  @Override
  public @Nullable Entry<K, V> floorEntry(@ParametricNullness K key) {
    return delegate().floorEntry(key);
  }

   * {@link #lowerEntry}, you may wish to override {@code lowerKey} to forward to this
   * implementation.
   */
  protected @Nullable K standardLowerKey(@ParametricNullness K key) {
    return keyOrNull(lowerEntry(key));
  }

  @Override
  public @Nullable Entry<K, V> floorEntry(@ParametricNullness K key) {
    return delegate().floorEntry(key);
  }