@ParametricNullness E upperBound,
      BoundType upperBoundType) {
    return tailMultiset(lowerBound, lowerBoundType).headMultiset(upperBound, upperBoundType);
  }

  @Override
  public SortedMultiset<E> tailMultiset(@ParametricNullness E lowerBound, BoundType boundType) {
    return delegate().tailMultiset(lowerBound, boundType);
  }

        delegate().subMultiset(lowerBound, lowerBoundType, upperBound, upperBoundType));
  }

  @Override
  public SortedMultiset<E> tailMultiset(@ParametricNullness E lowerBound, BoundType boundType) {
    return Multisets.unmodifiableSortedMultiset(delegate().tailMultiset(lowerBound, boundType));
  }

  @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0;

      @ParametricNullness E upperBound,
      BoundType upperBoundType) {
    return tailMultiset(lowerBound, lowerBoundType).headMultiset(upperBound, upperBoundType);
  }

  @Override
  public SortedMultiset<E> tailMultiset(@ParametricNullness E lowerBound, BoundType boundType) {
    return delegate().tailMultiset(lowerBound, boundType);
  }

    }

    @Override
    public @Nullable E ceiling(@ParametricNullness E e) {
      return getElementOrNull(multiset().tailMultiset(e, CLOSED).firstEntry());
    }

    @Override
    public @Nullable E higher(@ParametricNullness E e) {
      return getElementOrNull(multiset().tailMultiset(e, OPEN).firstEntry());
    }

    @Override
    public NavigableSet<E> descendingSet() {

    // These are checked elsewhere, but NullPointerTester wants them checked eagerly.
    checkNotNull(fromBoundType);
    checkNotNull(toBoundType);
    return tailMultiset(fromElement, fromBoundType).headMultiset(toElement, toBoundType);
  }

  abstract Iterator<Entry<E>> descendingEntryIterator();

  Iterator<E> descendingIterator() {

    assertEquals(Integer.MAX_VALUE, ms.headMultiset("a", CLOSED).size());

    assertEquals(3, ms.tailMultiset("c", CLOSED).size());
    assertEquals(Integer.MAX_VALUE, ms.tailMultiset("b", CLOSED).size());
    assertEquals(Integer.MAX_VALUE, ms.tailMultiset("a", CLOSED).size());
  }

  @J2ktIncompatible
  @GwtIncompatible // reflection

  public @Nullable Entry<E> pollLastEntry() {
    return forwardMultiset().pollFirstEntry();
  }

  @Override
  public SortedMultiset<E> headMultiset(E toElement, BoundType boundType) {
    return forwardMultiset().tailMultiset(toElement, boundType).descendingMultiset();
  }

  @Override
  public SortedMultiset<E> subMultiset(
      E fromElement, BoundType fromBoundType, E toElement, BoundType toBoundType) {
    return forwardMultiset()

                // values
                if (from == Bound.INCLUSIVE) {
                  multiset = multiset.tailMultiset(firstInclusive, BoundType.CLOSED);
                } else if (from == Bound.EXCLUSIVE) {
                  multiset = multiset.tailMultiset(firstExclusive, BoundType.OPEN);
                }

                if (to == Bound.INCLUSIVE) {

      BoundType toBoundType) {
    // These are checked elsewhere, but NullPointerTester wants them checked eagerly.
    checkNotNull(fromBoundType);
    checkNotNull(toBoundType);
    return tailMultiset(fromElement, fromBoundType).headMultiset(toElement, toBoundType);
  }

  abstract Iterator<Entry<E>> descendingEntryIterator();

  Iterator<E> descendingIterator() {

    return new TreeMultiset<>(
        rootReference,
        range.intersect(GeneralRange.upTo(comparator(), upperBound, boundType)),
        header);
  }

  @Override
  public SortedMultiset<E> tailMultiset(@ParametricNullness E lowerBound, BoundType boundType) {
    return new TreeMultiset<>(
        rootReference,
        range.intersect(GeneralRange.downTo(comparator(), lowerBound, boundType)),
        header);
  }