}

    @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) {
      return standardFloorKey(key);
    }

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

    @Override
    public @Nullable Entry<K, V> ceilingEntry(K key) {

   * #headMap(Object, boolean)}. If you override {@code headMap}, you may wish to override {@code
   * floorEntry} to forward to this implementation.
   */
  protected @Nullable Entry<K, V> standardFloorEntry(@ParametricNullness K key) {
    return headMap(key, true).lastEntry();
  }

  @Override
  public @Nullable K floorKey(@ParametricNullness K key) {
    return delegate().floorKey(key);
  }

   * #headMap(Object, boolean)}. If you override {@code headMap}, you may wish to override {@code
   * floorEntry} to forward to this implementation.
   */
  protected @Nullable Entry<K, V> standardFloorEntry(@ParametricNullness K key) {
    return headMap(key, true).lastEntry();
  }

  @Override
  public @Nullable K floorKey(@ParametricNullness K key) {
    return delegate().floorKey(key);
  }