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