*/
    @CanIgnoreReturnValue
    public Builder<E> addCopies(E element, int occurrences) {
      requireNonNull(contents); // see the comment on the field
      if (occurrences == 0) {
        return this;
      }
      if (buildInvoked) {
        contents = new ObjectCountHashMap<E>(contents);
        isLinkedHash = false;
      }