Financial: credit card number validation) 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 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:
/** 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