Count frequency = backingMap.get(element);
    int oldCount;
    if (frequency == null) {
      oldCount = 0;
      backingMap.put(element, new Count(occurrences));
    } else {
      oldCount = frequency.get();
      long newCount = (long) oldCount + (long) occurrences;
      checkArgument(newCount <= Integer.MAX_VALUE, "too many occurrences: %s", newCount);

    return delegate().setCount(element, count);
  }

  @CanIgnoreReturnValue
  @Override
  public boolean setCount(@ParametricNullness E element, int oldCount, int newCount) {
    return delegate().setCount(element, oldCount, newCount);
  }

  /**
   * A sensible definition of {@link #contains} in terms of {@link #count}. If you override {@link

      Multiset<E> self, @ParametricNullness E element, int oldCount, int newCount) {
    checkNonnegative(oldCount, "oldCount");
    checkNonnegative(newCount, "newCount");

    if (self.count(element) == oldCount) {
      self.setCount(element, newCount);
      return true;
    } else {
      return false;
    }
  }

  static <E extends @Nullable Object> Iterator<E> elementIterator(

      Multiset<E> self, @ParametricNullness E element, int oldCount, int newCount) {
    checkNonnegative(oldCount, "oldCount");
    checkNonnegative(newCount, "newCount");

    if (self.count(element) == oldCount) {
      self.setCount(element, newCount);
      return true;
    } else {
      return false;
    }
  }

  static <E extends @Nullable Object> Iterator<E> elementIterator(

    return delegate().setCount(element, count);
  }

  @CanIgnoreReturnValue
  @Override
  public boolean setCount(@ParametricNullness E element, int oldCount, int newCount) {
    return delegate().setCount(element, oldCount, newCount);
  }

  /**
   * A sensible definition of {@link #contains} in terms of {@link #count}. If you override {@link

    }

    @Override
    public int hashCode() {
      return standardHashCode();
    }

    @Override
    public boolean setCount(T element, int oldCount, int newCount) {
      return standardSetCount(element, oldCount, newCount);
    }

    @Override
    public int setCount(T element, int count) {
      return standardSetCount(element, count);
    }

    @Override

   *     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(@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);
        }