Credit Card Number Validation

/*
 * Name: Lu Liu
 * Date: 11/8/2015
 * Course Number: CSC-111
 * Course Name: Introduction to Java Programming
 * Problem Number:Problem 6.31(Credit Card Number Validation)
 * Email: lliu0001@student.stcc.edu
 * Problem Description: Credit Card Number Validation
 */
package chapter06;

import java.util.Scanner;

public class CreditCardValidation {
    public static void main(String args[]) {

        final String TITLE = "Credit Card Validator";
        final String CONTINUE_PROMPT = "Do this again? [y/N] ";
        System.out.println("Welcome to " + TITLE);
        Scanner sc = new Scanner(System.in);
        do {
            System.out.println("Enter a credit card number as a long integer: ");
            long ccn = sc.nextLong();
            sc.nextLine();
            if (isValid(ccn))
                System.out.println(ccn + " is valid");
            else
                System.out.println(ccn + " is invalid");
        } while (doThisAgain(sc, CONTINUE_PROMPT));
        sc.close();
        System.out.println("Thank you for using " + TITLE);
    }

    private static boolean doThisAgain(Scanner sc, String prompt) {
        System.out.print(prompt);
        String doOver = sc.nextLine();
        return doOver.equalsIgnoreCase("Y");
    }

    public static boolean isValid(long ccn) {
        if (ccn <= 0)
            return false;
        int size = getSize(ccn);
        if (size < 13 || size > 16)
            return false;
        if (!prefixMatched(ccn, 4) && !prefixMatched(ccn, 5) && !prefixMatched(ccn, 6) && !prefixMatched(ccn, 37))
            return false;
        return (sumOfDoubleEvenPlace(ccn) + sumOfOddPlace(ccn)) % 10 == 0;
    }

    public static int getSize(long d) {
        int count = 0;
        while (d > 0) {
            d = d / 10;
            count++;
        }
        return count;
    }

    public static int sumOfDoubleEvenPlace(long number) {
        int sum = 0;
        while (number > 0) {
            int last2Digits = (int) (number % 100);
            int evenDigit = last2Digits / 10;
            sum += getDigit(2 * evenDigit);
            number = number / 100;
        }
        return sum;
    }

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

    public static int sumOfOddPlace(long number) {
        int result = 0;
        while (number > 0) {
            result += (int) (number % 10);
            number = number / 100;
        }
        return result;
    }

    public static boolean prefixMatched(long number, int d) {
        if ((getPrefix(number, 1) == d) || (getPrefix(number, 2) == d))
            return true;
        else
            return false;
    }

    public static long getPrefix(long number, int k) {
        if (getSize(number) < k)
            return number;
        else {
            int size = (int) getSize(number);
            for (int i = 0; i < (size - k); i++) {
                number = number / 10;
            }
            return number;
        }
    }
}