code: public void addIterator(OJBIterator iterator)
      {
          /**
           * only add iterators that are not null and non-empty.
           */
          if (iterator != null)
          {
              if (iterator.hasNext())
              {
                  setNextIterator();
                  m_rsIterators.add(iterator);
              }
          }
      }
docs: use this method to construct the ChainingIterator
  iterator by iterator.