}

  @Override
  public @Nullable E lower(E element) {
    int index = headIndex(element, false) - 1;
    return (index == -1) ? null : elements.get(index);
  }

  @Override
  public @Nullable E floor(E element) {
    int index = headIndex(element, true) - 1;
    return (index == -1) ? null : elements.get(index);
  }

  @Override
  public @Nullable E ceiling(E element) {

   * simultaneously adopted and removed.
   */
  private val connections = ConcurrentLinkedQueue<RealConnection>()

  init {
    // Put a floor on the keep alive duration, otherwise cleanup will spin loop.
    require(keepAliveDuration > 0L) { "keepAliveDuration <= 0: $keepAliveDuration" }
  }

  fun idleConnectionCount(): Int =
    connections.count {

    }

    @Override
    public @Nullable V lower(@ParametricNullness V v) {
      return getSortedSetDelegate().lower(v);
    }

    @Override
    public @Nullable V floor(@ParametricNullness V v) {
      return getSortedSetDelegate().floor(v);
    }

    @Override
    public @Nullable V ceiling(@ParametricNullness V v) {
      return getSortedSetDelegate().ceiling(v);
    }

    @Override

    }

    @Override
    public @Nullable V lower(@ParametricNullness V v) {
      return getSortedSetDelegate().lower(v);
    }

    @Override
    public @Nullable V floor(@ParametricNullness V v) {
      return getSortedSetDelegate().floor(v);
    }

    @Override
    public @Nullable V ceiling(@ParametricNullness V v) {
      return getSortedSetDelegate().ceiling(v);
    }

    @Override

                  GNU LESSER GENERAL PUBLIC LICENSE
                       Version 2.1, February 1999

 Copyright (C) 1991, 1999 Free Software Foundation, Inc.
 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.

(This is the first released version of the Lesser GPL.  It also counts

    private @Nullable AvlNode<E> floor(Comparator<? super E> comparator, @ParametricNullness E e) {
      int cmp = comparator.compare(e, getElement());
      if (cmp > 0) {
        return (right == null) ? this : MoreObjects.firstNonNull(right.floor(comparator, e), this);
      } else if (cmp == 0) {
        return this;
      } else {
        return (left == null) ? null : left.floor(comparator, e);
      }
    }

      }
    }
    return null;
  }

  public @Nullable E ceiling(E e) {
    ImmutableSortedSet<E> set = tailSet(e, true);
    return !set.isEmpty() ? set.first() : null;
  }

  public @Nullable E floor(E e) {
    ImmutableSortedSet<E> set = headSet(e, true);
    return !set.isEmpty() ? set.last() : null;
  }

  public ImmutableSortedSet<E> headSet(E toElement, boolean inclusive) {
    checkNotNull(toElement);

    }

    @Override
    public @Nullable E lower(@ParametricNullness E e) {
      return delegate.lower(e);
    }

    @Override
    public @Nullable E floor(@ParametricNullness E e) {
      return delegate.floor(e);
    }

    @Override
    public @Nullable E ceiling(@ParametricNullness E e) {
      return delegate.ceiling(e);
    }

    @Override

    }

    @Override
    public @Nullable E lower(@ParametricNullness E e) {
      return delegate.lower(e);
    }

    @Override
    public @Nullable E floor(@ParametricNullness E e) {
      return delegate.floor(e);
    }

    @Override
    public @Nullable E ceiling(@ParametricNullness E e) {
      return delegate.ceiling(e);
    }

    @Override

          descendingSet = dS;
          return dS;
        }
        return descendingSet;
      }
    }

    @Override
    public @Nullable E floor(E e) {
      synchronized (mutex) {
        return delegate().floor(e);
      }
    }

    @Override
    public NavigableSet<E> headSet(E toElement, boolean inclusive) {
      synchronized (mutex) {