docs: private static String getFileTypeIconClass(String resourceTypeName, String fileName, boolean small) {
  
          if ((fileName != null) && fileName.contains(".")) {
              int last = fileName.lastIndexOf(".");
              if (fileName.length() > (last + 1)) {
                  String suffix = fileName.substring(fileName.lastIndexOf(".") + 1);
                  return getResourceSubTypeIconClass(resourceTypeName, suffix, small);
              }
          }
          return "";
  
      }