code: public boolean add (int oid)
      {
          // check for existence
          for (int ii = 0; ii < _size; ii++) {
              if (_oids[ii] == oid) {
                  return false;
              }
          }
  
          // make room if necessary
          if (_size+1 >= _oids.length) {
              expand();
          }
  
          // add the oid
          _oids[_size++] = oid;
          return true;
      }
docs: Adds the specified object id to the list if it is not already
  there.
  
  @return true if the object was added, false if it was already in
  the list.