JavaFX 8 added the @NamedArg annotation, to enable the FXMLLoader to instantiate classes without default constructors. There is no documentation on the annotation or its use in the Introduction to FXML document (https://docs.oracle.com/javase/8/javafx/api/javafx/fxml/doc-files/introduction_to_fxml.html) or in the FXMLLoader javadocs.

See also the StackOverflow question: http://stackoverflow.com/questions/26823157/what-is-the-purpose-of-namedarg-annotation-in-javafx-8