// Retrieve the paymentGroup's ListItem, and set its CSS class to "radio"
ListItem item = fieldset.getHtmlList().getLast();
item.setAttribute("class", "radio");
fieldset.add(new TextField("cardholderName"));
fieldset.add(new CreditCardField("cardNumber")).setRequired(true);
fieldset.add(new IntegerField("expiry"));
form.add(fieldset);
Submit ok = new Submit("ok", "OK");