JavaFX Fundamentals - Java 8 Recipes - page 587

newItem.setOnAction((ActionEvent event) -> {
if (LOGIN_DIALOG == null) {
LOGIN_DIALOG
= createLoginDialog(primaryStage, true);
}
LOGIN_DIALOG.sizeToScene();
LOGIN_DIALOG.show();
});
menu.getItems().add(newItem);
// add separator
menu.getItems().add(new SeparatorMenuItem());
// add non modal menu item
ToggleGroup modalGroup = new ToggleGroup();
RadioMenuItem nonModalItem = new RadioMenuItem();
nonModalItem.setToggleGroup(modalGroup);
nonModalItem.setText("Non Modal");
nonModalItem.setSelected(true);
nonModalItem.setOnAction((ActionEvent event) -> {
LOGIN_DIALOG
= createLoginDialog(primaryStage, false);
});
menu.getItems().add(nonModalItem);
// add modal selection
RadioMenuItem modalItem = new RadioMenuItem();
modalItem.setToggleGroup(modalGroup);
modalItem.setText("Modal");
modalItem.setSelected(true);
modalItem.setOnAction((ActionEvent event) -> {
LOGIN_DIALOG
= createLoginDialog(primaryStage, true);
});