Method isCreditCard

src/main/java/com/jdon/util/UtilValidate.java:857–899

Checks credit card number with Luhn Mod-10 test @param stPassed a string representing a credit card number @return true, if the credit card number passes the Luhn Mod-10 test, false otherwise

(String stPassed)

     * @return true, if the credit card number passes the Luhn Mod-10 test, false otherwise
     */
    public static boolean isCreditCard(String stPassed) {
        if (isEmpty(stPassed)) return defaultEmptyOK;
        String st = stripCharsInBag(stPassed, creditCardDelimiters);

        int sum = 0;
        int mul = 1;
        int l = st.length();

        // Encoding only works on cards with less than 19 digits
        if (l > 19) return (false);
        for (int i = 0; i < l; i++) {
            String digit = st.substring(l - i - 1, l - i);
            int tproduct = 0;

            try {
                tproduct = Integer.parseInt(digit, 10) * mul;
            } catch (Exception e) {
                Debug.logWarning(e.getMessage());
                return false;
            }
            if (tproduct >= 10)
                sum += (tproduct % 10) + 1;
            else
                sum += tproduct;
            if (mul == 1)
                mul++;
            else
                mul--;
        }
        // Uncomment the following line to help create credit card numbers
        // 1. Create a dummy number with a 0 as the last digit
        // 2. Examine the sum written out
        // 3. Replace the last digit with the difference between the sum and
        // the next multiple of 10.

        // document.writeln("<BR>Sum      = ",sum,"<BR>");
        // alert("Sum      = " + sum);

        if ((sum % 10) == 0)
            return true;
        else
            return false;
    }

    /** Checks to see if the cc number is a valid Visa number
     *