Write a program that gets user input such as the username, mode of payment, appropriate
credit card. After the user enters the appropriate values the Validation button validates the
values entered.
Answers
// Java program to check if a given credit
// card is valid or not.
import java.util.Scanner;
public class CreditCard {
// Main Method
public static void main(String[] args)
{
long number = 5196081888500645L;
System.out.println(number + " is " +
(isValid(number) ? "valid" : "invalid"));
}
// Return true if the card number is valid
public static boolean isValid(long number)
{
return (getSize(number) >= 13 &&
getSize(number) <= 16) &&
(prefixMatched(number, 4) ||
prefixMatched(number, 5) ||
prefixMatched(number, 37) ||
prefixMatched(number, 6)) &&
((sumOfDoubleEvenPlace(number) +
sumOfOddPlace(number)) % 10 == 0);
}
// Get the result from Step 2
public static int sumOfDoubleEvenPlace(long number)
{
int sum = 0;
String num = number + "";
for (int i = getSize(number) - 2; i >= 0; i -= 2)
sum += getDigit(Integer.parseInt(num.charAt(i) + "") * 2);
return sum;
}
// Return this number if it is a single digit, otherwise,
// return the sum of the two digits
public static int getDigit(int number)
{
if (number < 9)
return number;
return number / 10 + number % 10;
}
// Return sum of odd-place digits in number
public static int sumOfOddPlace(long number)
{
int sum = 0;
String num = number + "";
for (int i = getSize(number) - 1; i >= 0; i -= 2)
sum += Integer.parseInt(num.charAt(i) + "");
return sum;
}
// Return true if the digit d is a prefix for number
public static boolean prefixMatched(long number, int d)
{
return getPrefix(number, getSize(d)) == d;
}
// Return the number of digits in d
public static int getSize(long d)
{
String num = d + "";
return num.length();
}
// Return the first k number of digits from
// number. If the number of digits in number
// is less than k, return number.
public static long getPrefix(long number, int k)
{
if (getSize(number) > k) {
String num = number + "";
return Long.parseLong(num.substring(0, k));
}
return number;
}
}