The <clinit> methods of PlatformImpl and LauncherImpl check whether security manager is present and throw UnsupportedOperationException if it is. This check currently uses the deprecated System::getSecurityManager and should be rewritten to use reflection so that we aren't calling API that is deprecated for removal. Additionally, ensure that this check is done from all places where it is reasonably needed. In addition to the two current places, we should consider adding it to FXMLLoader in the javafx.fxml module, and ReflectUtil and MethodUtil in javafx.base. To avoid code duplication, create a utility method in javafx.base that does this check.