*     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

    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

    }
  }

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  public void testRemove_occurrences_0() {
    int oldCount = getMultiset().count(e0());
    assertEquals(
        "multiset.remove(E, 0) didn't return the old count",
        oldCount,
        getMultiset().remove(e0(), 0));
  }

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  public void testRemove_occurrences_negative() {

    }
  }

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  public void testRemove_occurrences_0() {
    int oldCount = getMultiset().count(e0());
    assertEquals(
        "multiset.remove(E, 0) didn't return the old count",
        oldCount,
        getMultiset().remove(e0(), 0));
  }

  @CollectionFeature.Require(SUPPORTS_REMOVE)
  public void testRemove_occurrences_negative() {

  @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);
        }

   * @deprecated Unsupported operation.
   */
  @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) {

   */
  @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 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) {