Try / Catch Into ActionListener - Detect Characters Other Than Alpha

I'm trying to place a try/catch into a Actionlistener that will detect other characters other than alpha.

private class printbuttonHandler implements ActionListener {
public void actionPerformed(ActionEvent e) {
//Object src = namesinput;
//String message = "Insert Message Here";
  notesinput.setText("");
JOptionPane.showMessageDialog(null, notesinput, "Receipt",
JOptionPane.PLAIN_MESSAGE);
}

I'm not even sure if I'm trying to place it in the correct area in the code. However I like to perform this prior to the receipt being displayed so if there a issue the user can correct this before the final receipt has been sent .......