code: public static String binaryToInternal(String clazz) {
      if (clazz.indexOf('/') >= 0 || clazz.indexOf('[') >= 0) {
        throw new IllegalArgumentException(String.format(Locale.ENGLISH, "'%s' is not a valid binary class name.", clazz));
      }
      return clazz.replace('.', '/');
    }
docs: Converts a binary class name (dotted) to the JVM internal one (slashed). Only accepts valid class names, no arrays.