// Query Operations

  /**
   * Returns the number of occurrences of {@code element} in this multiset.
   *
   * @param element the element to look for
   * @return the nonnegative number of occurrences of the element
   */
  @Override
  public int count(@CheckForNull Object element) {
    AtomicInteger existingCounter = Maps.safeGet(countMap, element);
    return (existingCounter == null) ? 0 : existingCounter.get();
  }

  /** Constructor for use by subclasses. */
  protected ForwardingListIterator() {}

  @Override
  protected abstract ListIterator<E> delegate();

  @Override
  public void add(@ParametricNullness E element) {
    delegate().add(element);
  }

  @Override
  public boolean hasPrevious() {
    return delegate().hasPrevious();
  }

  @Override
  public int nextIndex() {
    return delegate().nextIndex();
  }

    }
  }

  /**
   * A sensible definition of {@link #peek} in terms of {@link #element}. If you override {@link
   * #element}, you may wish to override {@link #peek} to forward to this implementation.
   *
   * @since 7.0
   */
  @CheckForNull
  protected E standardPeek() {
    try {
      return element();
    } catch (NoSuchElementException caught) {
      return null;
    }
  }

  /**

     * {@code list.size()} if there is no such element.
     *
     * <p>Note that the return value will be {@code >= 0} if and only if there is an element of the
     * list that compares as equal to the key.
     *
     * <p>This is equivalent to the behavior of {@link java.util.Collections#binarySearch(List,

  public void testHashCode_containingNull() {
    Collection<E> elements = getSampleElements(getNumElements() - 1);
    int expectedHashCode = 0;
    for (E element : elements) {
      expectedHashCode += ((element == null) ? 0 : element.hashCode());
    }

    elements.add(null);
    collection = getSubjectGenerator().create(elements.toArray());
    assertEquals(

      for (int i = 0; i < 100; i++) {
        Element element = Element.values()[random.nextInt(range)];
        elements.add(element);
        queue.add(element);
      }
      Iterator<Element> queueIterator = queue.iterator();
      int remaining = queue.size();
      while (queueIterator.hasNext()) {
        Element element = queueIterator.next();
        remaining--;

    if (occurrences == 0) {
      return count(element);
    }
    checkArgument(occurrences > 0, "occurrences cannot be negative: %s", occurrences);
    int entryIndex = backingMap.indexOf(element);
    if (entryIndex == -1) {
      backingMap.put(element, occurrences);
      size += occurrences;
      return 0;
    }
    int oldCount = backingMap.getValue(entryIndex);

    Hash {
      @Override
      Map<Element, Element> create(Collection<Element> keys) {
        Map<Element, Element> map = Maps.newHashMap();
        for (Element element : keys) {
          map.put(element, element);
        }
        return map;
      }
    },
    LinkedHM {
      @Override
      Map<Element, Element> create(Collection<Element> keys) {
        Map<Element, Element> map = Maps.newLinkedHashMap();

    collection = getSubjectGenerator().create(arrayAndDuplicate.elements);
    E duplicate = arrayAndDuplicate.duplicate;

    int firstIndex = getList().indexOf(duplicate);
    int initialSize = getList().size();
    assertTrue("remove(present) should return true", getList().remove(duplicate));
    assertTrue(
        "After remove(duplicate), a list should still contain the duplicate element",
        getList().contains(duplicate));
    assertFalse(

        double partition = array[from + 1]; // Choose partitioning element.
        while (true) {
          // Skip the elements smaller than the partition.
          do {
            low++;
          } while (array[low] < partition);

          // Skip the elements larger than the partition.
          do {
            high--;
          } while (array[high] > partition);