ToggleGroup genderGroup = new ToggleGroup();
male.setToggleGroup(genderGroup);
female.setToggleGroup(genderGroup);
genderGroup.selectedToggleProperty().addListener(
(observable, oldToggle, newToggle) -> {
if (newToggle == male) {
gender = 'm';
} else if (newToggle == female) {
gender = 'f';
} else {
gender = '?';
}
}
);