code: public FilterCellSlowStr findNextCell(String nextValue) {
          if (nextCell == null) {
              return null;
          }
          return nextCell.get(nextValue);
      }
docs: Find the next cell, for a given string, which may come after this cell
  in the address tree.
  
  @param nextValue
  The next string the URL Address that is to be tested
  for inclusion in the address tree
  @return null if the nextValue does not have another cell connected to this
  cell in the tree. Otherwise return the next cell in the tree that
  is represented
  by nextValue.