public K lowerKey(@ParametricNullness K key) {
    return Maps.keyOrNull(lowerEntry(key));
  }

  @Override
  @CheckForNull
  public K floorKey(@ParametricNullness K key) {
    return Maps.keyOrNull(floorEntry(key));
  }

  @Override
  @CheckForNull
  public K ceilingKey(@ParametricNullness K key) {
    return Maps.keyOrNull(ceilingEntry(key));
  }

  @Override
  @CheckForNull

  public K lowerKey(@ParametricNullness K key) {
    return Maps.keyOrNull(lowerEntry(key));
  }

  @Override
  @CheckForNull
  public K floorKey(@ParametricNullness K key) {
    return Maps.keyOrNull(floorEntry(key));
  }

  @Override
  @CheckForNull
  public K ceilingKey(@ParametricNullness K key) {
    return Maps.keyOrNull(ceilingEntry(key));
  }

  @Override
  @CheckForNull

    }
    if (oldEntryForValue != null) {
      oldEntryForValue.prevInKeyInsertionOrder = null;
      oldEntryForValue.nextInKeyInsertionOrder = null;
    }
    rehashIfNecessary();
    return Maps.keyOrNull(oldEntryForValue);
  }

  private void rehashIfNecessary() {
    @Nullable BiEntry<K, V>[] oldKToV = hashTableKToV;
    if (Hashing.needsResizing(size, oldKToV.length, LOAD_FACTOR)) {

  @Override
  @CheckForNull
  public K lowerKey(K key) {
    return keyOrNull(lowerEntry(key));
  }

  @Override
  @CheckForNull
  public Entry<K, V> floorEntry(K key) {
    return headMap(key, true).lastEntry();
  }

  @Override
  @CheckForNull
  public K floorKey(K key) {
    return keyOrNull(floorEntry(key));
  }

  @Override
  @CheckForNull

  @Override
  @CheckForNull
  public K lowerKey(K key) {
    return keyOrNull(lowerEntry(key));
  }

  @Override
  @CheckForNull
  public Entry<K, V> floorEntry(K key) {
    return headMap(key, true).lastEntry();
  }

  @Override
  @CheckForNull
  public K floorKey(K key) {
    return keyOrNull(floorEntry(key));
  }

  @Override
  @CheckForNull

      return map().higherKey(e);
    }

    @Override
    @CheckForNull
    public K pollFirst() {
      return keyOrNull(map().pollFirstEntry());
    }

    @Override
    @CheckForNull
    public K pollLast() {
      return keyOrNull(map().pollLastEntry());
    }

    @Override
    public NavigableSet<K> descendingSet() {
      return map().descendingKeySet();

      return map().higherKey(e);
    }

    @Override
    @CheckForNull
    public K pollFirst() {
      return keyOrNull(map().pollFirstEntry());
    }

    @Override
    @CheckForNull
    public K pollLast() {
      return keyOrNull(map().pollLastEntry());
    }

    @Override
    public NavigableSet<K> descendingSet() {
      return map().descendingKeySet();