checkArgument(occurrences <= Integer.MAX_VALUE - frequency);
      backingMap.put(element, frequency + occurrences);
      return frequency;
    }

    @Override
    Iterator<E> elementIterator() {
      return Multisets.elementIterator(entryIterator());
    }

    @Override
    Iterator<Entry<E>> entryIterator() {
      Iterator<Map.Entry<E, Integer>> backingEntries = backingMap.entrySet().iterator();

    @Override
    Multiset<E> multiset() {
      return AbstractMultiset.this;
    }

    @Override
    public Iterator<E> iterator() {
      return elementIterator();
    }
  }

  abstract Iterator<E> elementIterator();

  @LazyInit private transient @Nullable Set<Entry<E>> entrySet;

  @Override
  public Set<Entry<E>> entrySet() {
    Set<Entry<E>> result = entrySet;

      if (counts[toRemove] > 0) {
        distinctElements--;
        size -= counts[toRemove];
        counts[toRemove] = 0;
      }
      toRemove = -1;
    }
  }

  @Override
  Iterator<E> elementIterator() {
    return new Itr<E>() {
      @Override
      E output(int index) {
        return enumConstants[index];
      }
    };
  }

  @Override
  Iterator<Entry<E>> entryIterator() {

      this.multiset = multiset;
    }

    @Override
    final SortedMultiset<E> multiset() {
      return multiset;
    }

    @Override
    public Iterator<E> iterator() {
      return Multisets.elementIterator(multiset().entrySet().iterator());
    }

    @Override
    public Comparator<? super E> comparator() {
      return multiset().comparator();
    }

    @Override

      entryIndex = backingMap.nextIndexAfterRemove(entryIndex, toRemove);
      toRemove = -1;
      expectedModCount = backingMap.modCount;
    }
  }

  @Override
  final Iterator<E> elementIterator() {
    return new Itr<E>() {
      @Override
      @ParametricNullness
      E result(int entryIndex) {
        return backingMap.getKey(entryIndex);
      }
    };
  }

  @Override