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.");
  }
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.");
  }
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." ) ; }
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)
Returns whether or not the class is part of the JDK ( rt . jar ) .