/** Custom error message */
  public void showErrorMsg(String title, String msg) {

    JOptionPane.showMessageDialog(this, msg, title, JOptionPane.ERROR_MESSAGE);
  }
  /** Observer method to show an error message */
  public void showErrorMsg(Throwable t) {

    JOptionPane.showMessageDialog(this, t, "Error", JOptionPane.ERROR_MESSAGE);
  }