public List<SelectItem> getCustomerClassList() {
   if (customerClassList == null) {
     customerClassList = new ArrayList<SelectItem>();
     customerClassList.add(new SelectItem("", "--select--"));
     for (CustomerClass customerClass : CustomerClass.values()) {
       customerClassList.add(new SelectItem(customerClass.name(), customerClass.name()));
     }
   }
   return customerClassList;
 }