code: public void swap( int src, int dest ) {
          List<Rule> rules = featureTypeStyle.rules();
          if (src >= 0 && src < rules.size() && dest >= 0 && dest < rules.size()) {
              Collections.swap(rules, src, dest);
              Collections.swap(rulesWrapperList, src, dest);
          }
      }
docs: Swap two elements of the list.
  
  @param src the position first element.
  @param dest the position second element.