checkNonnegative(count, "count");
    int oldCount = (count == 0) ? backingMap.remove(element) : backingMap.put(element, count);
    size += (count - oldCount);
    return oldCount;
  }

  @Override
  public final boolean setCount(@ParametricNullness E element, int oldCount, int newCount) {
    checkNonnegative(oldCount, "oldCount");
    checkNonnegative(newCount, "newCount");

   *     was indeed modified, unless {@code oldCount == newCount}.
   * @throws IllegalArgumentException if {@code oldCount} or {@code newCount} is negative
   * @throws NullPointerException if {@code element} is null and the implementation does not permit
   *     null elements. Note that if {@code oldCount} and {@code newCount} are both zero, the

   *     was indeed modified, unless {@code oldCount == newCount}.
   * @throws IllegalArgumentException if {@code oldCount} or {@code newCount} is negative
   * @throws NullPointerException if {@code element} is null and the implementation does not permit
   *     null elements. Note that if {@code oldCount} and {@code newCount} are both zero, the

  @CanIgnoreReturnValue
  @Override
  public boolean setCount(@ParametricNullness E element, int oldCount, int newCount) {
    checkNonnegative(newCount, "newCount");
    checkNonnegative(oldCount, "oldCount");
    checkArgument(range.contains(element));

    AvlNode<E> root = rootReference.get();
    if (root == null) {
      if (oldCount == 0) {
        if (newCount > 0) {
          add(element, newCount);
        }

   */
  @CanIgnoreReturnValue
  @Override
  public boolean setCount(E element, int expectedOldCount, int newCount) {
    checkNotNull(element);
    checkNonnegative(expectedOldCount, "oldCount");
    checkNonnegative(newCount, "newCount");

    AtomicInteger existingCounter = safeGet(countMap, element);
    if (existingCounter == null) {
      if (expectedOldCount != 0) {
        return false;

   */
  @CanIgnoreReturnValue
  @Override
  public boolean setCount(E element, int expectedOldCount, int newCount) {
    checkNotNull(element);
    checkNonnegative(expectedOldCount, "oldCount");
    checkNonnegative(newCount, "newCount");

    AtomicInteger existingCounter = safeGet(countMap, element);
    if (existingCounter == null) {
      if (expectedOldCount != 0) {
        return false;

        return 0;
      }

      int oldCount = values.size();
      if (occurrences >= oldCount) {
        values.clear();
      } else {
        Iterator<V> iterator = values.iterator();
        for (int i = 0; i < occurrences; i++) {
          iterator.next();
          iterator.remove();
        }
      }
      return oldCount;
    }

    @Override
    public void clear() {

        return 0;
      }

      int oldCount = values.size();
      if (occurrences >= oldCount) {
        values.clear();
      } else {
        Iterator<V> iterator = values.iterator();
        for (int i = 0; i < occurrences; i++) {
          iterator.next();
          iterator.remove();
        }
      }
      return oldCount;
    }

    @Override
    public void clear() {