/**
  * @return The card number string consisting of all but the last four digits replaced with bullet
  *     ('•').
  */
 public String getRedactedCardNumber() {
   if (cardNumber != null) {
     String redacted = "";
     if (cardNumber.length() > 4) {
       redacted += String.format("%" + (cardNumber.length() - 4) + "s", "").replace(' ', '\u2022');
     }
     redacted += getLastFourDigitsOfCardNumber();
     return CreditCardNumber.formatString(redacted, false, CardType.fromCardNumber(cardNumber));
   } else {
     return "";
   }
 }
 /** @return A string suitable for display, with spaces inserted for readability. */
 public String getFormattedCardNumber() {
   return CreditCardNumber.formatString(cardNumber);
 }