code: private static Map<String, String> getRankMap(Utils utils, List<? extends Element> params){
          if (params == null) {
              return null;
          }
          HashMap<String, String> result = new HashMap<>();
          int rank = 0;
          for (Element e : params) {
              String name = utils.isTypeParameterElement(e)
                      ? utils.getTypeName(e.asType(), false)
                      : utils.getSimpleName(e);
              result.put(name, String.valueOf(rank));
              rank++;
          }
          return result;
      }
docs: Given an array of <code>Parameter</code>s, return
  a name/rank number map.  If the array is null, then
  null is returned.
  @param params The array of parameters (from type or executable member) to
  check.
  @return a name-rank number map.