JavaFX: Red border for text field

Question

I have a form with text fields and I want to give them a red border if I click on \"save\" but e.g. nothing was input in required fields, letters for the \"birthday\" field,

Answer 1

With this it now works pefectly fine (it doesn't even need "setUpValidation"):

public void initialize(URL arg0, ResourceBundle arg1) {
    removeRed(tfFirstName);
    removeRed(tfLastName);
}

public void OKButtonClicked() {
    try{
        //also: call validation class here
        removeRed(tfFirstName);
        removeRed(tfLastName);
    } catch(ValidationException e) {
        setRed(tfFirstName);
        setRed(tfLastName);
    }

}

private void setRed(TextField tf) {
    ObservableList styleClass = tf.getStyleClass();

    if(!styleClass.contains("tferror")) {
        styleClass.add("tferror");
    }
}


private void removeRed(TextField tf) {
    ObservableList styleClass = tf.getStyleClass();
    styleClass.removeAll(Collections.singleton("tferror"));
}

And in the css I added the following (unfortunately it didn't change the border width with "-fx-border-width: 2px" anymore):

.tferror {  
     -fx-text-box-border: red ;
     -fx-focus-color: red ;   
}