@Override
    public void insertUpdate(DocumentEvent de) {
    //Skip to the next TextField if input is valid and complete
            try {
                String text = de.getDocument().getText(0, de.getDocument().getLength());
                int inputNumber = Integer.parseInt(text);
                if ((inputNumber >= 2 && inputNumber <= 15) || text.equals("01") || text.equals("00")) {
                    KeyboardFocusManager manager = KeyboardFocusManager.getCurrentKeyboardFocusManager();
                    manager.focusNextComponent();
                }
            } catch (NumberFormatException e) {
                //Do nothing
            } catch (BadLocationException ex) {
            Logger.getLogger(SubjectUI.class.getName()).log(Level.SEVERE, "Why is this happening?", ex);
        }
    }