* @return String
   */
  public static String fileExtension(String file) {
    { int start = 0;
      int end = Stella.NULL_INTEGER;

      while (Native.string_position(file, Stella.TYPE_SEPARATOR, start) != Stella.NULL_INTEGER) {
        end = Native.string_position(file, Stella.TYPE_SEPARATOR, start);
        start = end + 1;
      }
      if (end == Stella.NULL_INTEGER) {
        return (null);
      }
      else if (Native.string_position(file, Stella.directorySeparatorForFile(file), end) != Stella.NULL_INTEGER) {
        return (null);
      }
      else {
        return (Native.string_subsequence(file, end, Stella.NULL_INTEGER));
      }
    }
  }