code: public static String getSuffix(File file) {
  
          String filename = file.getName();
          int index = filename.lastIndexOf(".");
          if (index != -1) {
              return filename.substring(index + 1);
          }
  
          return filename;
      }
docs: Returns a suffix string from a File.
  
  @param file The file to know the suffix.
  
  @return A suffix string