code: public static boolean inJdk(@ClassGetName String classname) {
      return classname.startsWith("java.")
          || classname.startsWith("com.oracle.")
          || classname.startsWith("com.sun.")
          || classname.startsWith("javax.")
          || classname.startsWith("jdk.")
          || classname.startsWith("org.ietf.")
          || 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 the format of Class.getName(); the class should not be
  an array
  @return true iff the class is in a package that is in the JDK (rt.jar)