DDescription Credit card numbers follow certain patterns. A credit card number m
ID: 3688262 • Letter: D
Question
DDescription Credit card numbers follow certain patterns. A credit card number must have between 13 and 16 digits. It must start with: 4 for Visa cards 5 for Master cards 37 for American Express cards 6 for Discover cards In 1954, Hans Luhn of IBM proposed an algorithm for validating credit card numbers. The algorithm is useful to determine whether a card number is entered correctly or whether a credit card is scanned correctly by a scanner. All credit card numbers are generated following this validity check, commonly known as the Luhn check or the Mod 10 check, which can be described as follows (for illustration, consider the card number 4388576018402626): 1. Double every second digit from right to left. If the doubling of a digit results in a two-digit number, add up the two digits to get a single-digit number. 2*2= 4 2*2= 4 4*2= 8 1*2= 2 6 * 2 = 12 (1 + 2 = 3) 5 * 2 = 10 (1 + 0 = 1) 8 * 2 = 16 (1 + 6 = 7) 4*2= 8 2. Now add all single-digit numbers from Step 1. 4 + 4 + 8 + 2 + 3 + 1 + 7 + 8 = 37 3. Add all digits in the odd places from right to left in the card number. 6 + 6 + 0 + 8 + 0 + 7 + 8 + 3 = 38 4. Sum the results from Step 2 and Step 3. 37 + 38 = 75 5. If the result from Step 4 is divisible by 10, the card number is valid; otherwise, it is invalid. For example, the number 4388576018402626 is invalid, but the number 4388576018410707 is valid. Write a program that prompts the user to enter a credit card number as a long integer. Display whether the number is valid or invalid. Design your program to use the following methods: 1 Following Methods can be used to write your program: /** Return true if the card number is valid */ public static boolean isValid(long number) /** Get the result from Step 2 */ public static int sumOfDoubleEvenPlace(long number) /** Return this number if it is a single digit, otherwise, return the sum of the two digits */ public static int getDigit(int number) /** Return sum of odd place digits in number */ public static int sumOfOddPlace(long number) /** Return true if the digit d is a prefix for number */ public static boolean prefixMatched(long number, int d) /** Return the number of digits in d */ public static int getSize(long d) /** 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) Example Output: Please enter a Credit Card Number: 4388576018410707 The CC Number: 4388576018410707 is valid. Please enter a Credit Card Number: 4388576018402626 The CC Number: 4388576018402626 is invalid. (The program cannot be in main method)Explanation / Answer
import java.util.Scanner;
/**
* @author Srinivas Palli
*
*/
public class CreditCardValidation {
/**
*
* Return true if the card number is valid
*
* @param number
* @return
*/
public static boolean isValid(long number) {
int total = sumOfDoubleEvenPlace(number) + sumOfOddPlace(number);
if ((total % 10 == 0) && (prefixMatched(number, 1) == true)
&& (getSize(number) >= 13) && (getSize(number) <= 16)) {
return true;
} else {
return false;
}
}
/**
* Return this number if it is a single digit, otherwise, return the sum of
* the two digits
*
* @param number
* @return
*/
public static int getDigit(int number) {
if (number <= 9) {
return number;
} else {
int firstDigit = number % 10;
int secondDigit = (int) (number / 10);
return firstDigit + secondDigit;
}
}
/**
* Return sum of odd place digits in number
*
* @param number
* @return
*/
public static int sumOfOddPlace(long number) {
int result = 0;
while (number > 0) {
result += (int) (number % 10);
number = number / 100;
}
return result;
}
/**
*
* @param number
* @return
*/
public static int sumOfDoubleEvenPlace(long number) {
int result = 0;
long temp = 0;
while (number > 0) {
temp = number % 100;
result += getDigit((int) (temp / 10) * 2);
number = number / 100;
}
return result;
}
/**
* Return true if the digit d is a prefix for number
*
* @param number
* @param d
* @return
*/
public static boolean prefixMatched(long number, int d) {
if ((getPrefix(number, d) == 4) || (getPrefix(number, d) == 5)
|| (getPrefix(number, d) == 3)) {
if (getPrefix(number, d) == 3) {
System.out.println(" Visa Card ");
} else if (getPrefix(number, d) == 5) {
System.out.println(" Master Card ");
} else if (getPrefix(number, d) == 3) {
System.out.println(" American Express Card ");
}
return true;
} else {
return false;
}
}
/**
* Return the number of digits in d
*
* @param d
* @return
*/
public static int getSize(long d) {
int count = 0;
while (d > 0) {
d = d / 10;
count++;
}
return count;
}
/**
* Return the first k number of digits from number. If the * number of
* digits in number is less than k, return number.
*
* @param number
* @param k
* @return
*/
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;
}
}
/**
* @param args
*/
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.print("Please enter a Credit Card Number: ");
long input = sc.nextLong();
if (isValid(input) == true) {
System.out.println("The CC Number: "+input + " is Valid. ");
} else {
System.out.println("The CC Number: "+input + " is Invalid. ");
}
}
}
OUTPUT:
Please enter a Credit Card Number: 4388576018410707
The CC Number: 4388576018410707 is Valid.
Please enter a Credit Card Number: 4388576018402626
The CC Number: 4388576018402626 is Invalid.
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