Credit card type and validation

Question

I would like to run a program that can determine the validation and type of credit card number based of number entered. Compiler shows notification that there is an error in my coding but I cannot detect where is it. The program is also cannot be run. Below is the coding,

    import java.util.*;

    public class CreditCard {

        public static void main(String args[]) {
                String CType;(String number) {
                    if (number.startsWith("4"))
                        return "Visa";
                    else if (number.startsWith("5"))
                        return "MasterCard";
                    else if (number.startsWith("6"))
                        return "Discover";
                    else if (number.startsWith("37"))
                        return "American Express";
                    else
                        return "Unknown type";
                };
            Scanner input = new Scanner(System.in);

            System.out.println("Enter a credit card number: ");
            long number = input.nextLong();

            long total = sumOfEvenPlaces(number) + (sumOfOddPlaces(number)*2);

            if (isValid(total)) {
                System.out.println("The "+CType+" card number is valid");
            } else {
                System.out.println("The "+CType+" card number is invalid.");
            }
        }



        public static boolean isValid(long total) {
            if (total % 10 != 0) {
            } else {
                        return true;
                }
            return false;
        }

        public static int sumOfEvenPlaces(long number) {
            int sum = 0;
            int remainder;
            while (number % 10 != 0 || number / 10 != 0) {
                remainder = (int) (number % 10);

                sum = sum + getDigit(remainder * 2);
                number /= 100;
            }
            return sum;
        }

        public static int getDigit(int number) {
            if (number > 9) {
                return (number % 10 + number / 10);
            } 
            return number;
        }

        public static int sumOfOddPlaces(long number) {
            int sum = 0;
            int remainder;
            number /= 10;
            while (number % 10 != 0 || number / 10 != 0) {
                remainder = (int) (number % 10);
                sum = sum + getDigit(remainder * 2);
                number /= 100;
            }
            return sum;
        }
    }

user_2317829 · Answer

This may be more along the lines of what you're trying to do:

    public static void main(final String args[])
    {
        String cType = null;

        System.out.println("Enter a credit card number: ");
        final Scanner input = new Scanner(System.in);
        final String cardNumber = input.next();

        if (cardNumber.startsWith("4"))
        {
            cType = "Visa";
        }
        else if (cardNumber.startsWith("5"))
        {
            cType =  "MasterCard";
        }
        else if (cardNumber.startsWith("6"))
        {
            cType =  "Discover";
        }
        else if (cardNumber.startsWith("37"))
        {
            cType =  "American Express";
        }
        else
        {
            cType =  "Unknown type";
        }

        final long total = sumOfEvenPlaces(Long.valueOf(cardNumber)) + (sumOfOddPlaces(Long.valueOf(cardNumber)) * 2);

        if (isValid(total))
        {
            System.out.println("The " + cType + " card number is valid");
        }
        else
        {
            System.out.println("The " + cType + " card number is invalid.");
        }
    }

On a stylistic note, CType should start with a lower case letter (e.g. cType). You'll have to experiment with the use of Scanner as well as I'm not sure my implementation will do what you're looking for.

Credit card type and validation

2 Answers