* {@code floorEntry}, you may wish to override {@code floorKey} to forward to this
   * implementation.
   */
  protected @Nullable K standardFloorKey(@ParametricNullness K key) {
    return keyOrNull(floorEntry(key));
  }

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

   * {@code floorEntry}, you may wish to override {@code floorKey} to forward to this
   * implementation.
   */
  protected @Nullable K standardFloorKey(@ParametricNullness K key) {
    return keyOrNull(floorEntry(key));
  }

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