return backingMap.getEntry(entryIndex);
      }
    };
  }

  /** Allocation-free implementation of {@code target.addAll(this)}. */
  void addTo(Multiset<? super E> target) {
    checkNotNull(target);
    for (int i = backingMap.firstIndex(); i >= 0; i = backingMap.nextIndex(i)) {
      target.add(backingMap.getKey(i), backingMap.getValue(i));
    }
  }

  @Override
  final int distinctElements() {

  /*
   * Cache the size for efficiency. Using a long lets us avoid the need for
   * overflow checking and ensures that size() will function correctly even if
   * the multiset had once been larger than Integer.MAX_VALUE.
   */
  private transient long size;

  /** Standard constructor. */
  protected AbstractMapBasedMultiset(Map<E, Count> backingMap) {
    checkArgument(backingMap.isEmpty());