Add a listener in textProperty, when there is a change in text, verify if the same is valid, if invalid set empty in text.

see:

textProperty().addListener(new ChangeListener<String>() {
    private boolean inProgress;
    @Override public void changed(ObservableValue<? extends String> observable, String oldValue, String newValue) {
        if (inProgress) {
            return;
        }
        inProgress = true;
        try {
            thow new Exception(); //here logic code for validation
        } catch (ParseException e) {
            setText("");
        }
        inProgress = false;
    }
});


In the case above the TextField should be always empty.

But it's not what happens. Always gets a letter.