JSpinnerの文字列を非表示にする

private static JSpinner makeSpinner1(SpinnerNumberModel m) {
  JSpinner s = new JSpinner(m);
  JFormattedTextField ftf = getJFormattedTextField(s);
  DecimalFormatSymbols dfs = new DecimalFormatSymbols();
  ftf.setFormatterFactory(makeFFactory(dfs));
  ftf.setDisabledTextColor(UIManager.getColor("TextField.disabledColor"));
  return s;
}

private static JSpinner makeSpinner2(SpinnerNumberModel m) {
  JSpinner s = new JSpinner(m);
  JFormattedTextField ftf = getJFormattedTextField(s);
  DecimalFormatSymbols dfs = new DecimalFormatSymbols();
  dfs.setNaN(" ");
  ftf.setFormatterFactory(makeFFactory(dfs));
  return s;
}