code: public static String getExtension(String file)
      {
          Check.notNull(file);
  
          String ext = Constant.EMPTY_STRING;
          final int i = file.lastIndexOf(Constant.DOT);
          if (i >= 0 && i < file.length() - 1)
          {
              ext = file.substring(i + 1).toLowerCase(Locale.ENGLISH);
          }
          return ext;
      }
docs: Get extension from a string (search first dot).
  
  @param file The filename (must not be <code>null</code>).
  @return The extension without dot.
  @throws LionEngineException If invalid arguments.