code: public static boolean inJdkInternalform(@InternalForm String classname) {
      return classname.startsWith("java/")
          || classname.startsWith("com/oracle/")
          || classname.startsWith("com/sun/")
          || classname.startsWith("javax/")
          || classname.startsWith("jdk/")
          || classname.startsWith("org/ietj/")
          || classname.startsWith("org/jcp/")
          || classname.startsWith("org/omg/")
          || classname.startsWith("org/w3c/")
          || classname.startsWith("org/xml/")
          || classname.startsWith("sun/")
          || classname.startsWith("sunw/");
    }
docs: Returns whether or not the class is part of the JDK (rt.jar).
  
  @param classname the class to test, in internal form
  @return true iff the class is part of the JDK (rt.jar)