return setCountImpl(this, element, count);
  }

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

  // Bulk Operations

  /**
   * {@inheritDoc}
   *
   * <p>This implementation is highly efficient when {@code elementsToAdd} is itself a {@link
   * Multiset}.

      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);
      frequency.add(occurrences);
    }
    size += occurrences;
    return oldCount;
  }

  @CanIgnoreReturnValue
  @Override

  static <E extends @Nullable Object> boolean setCountImpl(
      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> boolean setCountImpl(
      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;
    }
  }

   * @param newCount the desired count of the element in this multiset
   * @return {@code true} if the condition for modification was met. This implies that the multiset
   *     was indeed modified, unless {@code oldCount == newCount}.
   * @throws IllegalArgumentException if {@code oldCount} or {@code newCount} is negative

   * @param newCount the desired count of the element in this multiset
   * @return {@code true} if the condition for modification was met. This implies that the multiset
   *     was indeed modified, unless {@code oldCount == newCount}.
   * @throws IllegalArgumentException if {@code oldCount} or {@code newCount} is negative

      count += values.length();
      return this;
    }

    private void ensureRoomFor(int numberToAdd) {
      int newCount = count + numberToAdd; // TODO(kevinb): check overflow now?
      if (newCount > array.length) {
        array = Arrays.copyOf(array, expandedCapacity(array.length, newCount));
      }
    }

    // Unfortunately this is pasted from ImmutableCollection.Builder.

      count += values.length();
      return this;
    }

    private void ensureRoomFor(int numberToAdd) {
      int newCount = count + numberToAdd; // TODO(kevinb): check overflow now?
      if (newCount > array.length) {
        array = Arrays.copyOf(array, expandedCapacity(array.length, newCount));
      }
    }

    // Unfortunately this is pasted from ImmutableCollection.Builder.

   */
  @CanIgnoreReturnValue
  @Deprecated
  @Override
  @DoNotCall("Always throws UnsupportedOperationException")
  public final boolean setCount(E element, int oldCount, int newCount) {
    throw new UnsupportedOperationException();
  }

  @GwtIncompatible // not present in emulated superclass
  @Override
  int copyIntoArray(@Nullable Object[] dst, int offset) {

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

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

    @Override
    public Set<E> elementSet() {
      synchronized (mutex) {
        if (elementSet == null) {