SetBuilderImpl<E> add(E e) {
      checkNotNull(e);
      if (hashTable == null) {
        if (distinct == 0) {
          addDedupedElement(e);
          return this;
        } else {
          ensureTableCapacity(dedupedElements.length);
          E elem = dedupedElements[0];
          distinct--;
          return insertInHashTable(elem).add(e);
        }
      }
      return insertInHashTable(e);
    }