abstract ImmutableSortedSet<E> tailSetImpl(E fromElement, boolean inclusive);

  /** @since 12.0 */
  @GwtIncompatible // NavigableSet
  @Override
  @CheckForNull
  public E lower(E e) {
    return Iterators.<@Nullable E>getNext(headSet(e, false).descendingIterator(), null);
  }

  /** @since 12.0 */
  @Override
  @CheckForNull
  public E floor(E e) {

import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.collect.SortedLists.KeyAbsentBehavior.NEXT_HIGHER;
import static com.google.common.collect.SortedLists.KeyAbsentBehavior.NEXT_LOWER;
import static com.google.common.collect.SortedLists.KeyPresentBehavior.ANY_PRESENT;
import static java.util.Objects.requireNonNull;

import com.google.common.annotations.Beta;

    int index =
        SortedLists.binarySearch(
            ranges,
            Range::lowerBound,
            Cut.belowValue(key),
            KeyPresentBehavior.ANY_PRESENT,
            KeyAbsentBehavior.NEXT_LOWER);
    if (index == -1) {
      return null;
    } else {
      Range<K> range = ranges.get(index);
      return range.contains(key) ? values.get(index) : null;
    }
  }

  @Override