* be an unchanging snapshot of the count at the time the entry was retrieved, or a live view of
     * the current count of the element in the multiset, depending on the implementation. Note that
     * in the former case, this method can never return zero, while in the latter, it will return
     * zero if all occurrences of the element were since removed from the multiset.
     *
     * @return the count of the element; never negative