Credit Card Mod10 校验

最新推荐文章于 2021-09-08 14:01:42 发布

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本文介绍了一种用于验证信用卡号码有效性的Luhn算法（MOD10）。通过实例详细展示了该算法的具体步骤，并提供了四种不同的实现方式。此外，还列举了常见信用卡类型及其前缀和长度。

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以下是几种Mod10的实现。第一种最为简洁，最后一种最为易懂。你喜欢哪一种？

/**

* Check whether a credit card number is valid or not according to the Luhn algorithm (MOD10).

*

* (Getting from http://en.wikipedia.org/wiki/Luhn_algorithm)

* 1. Counting from the check digit, which is the rightmost, and moving left, double the value of every second digit.

* 2. Sum the digits of the products together with the undoubled digits from the original number.

* 3. If the total ends in 0 (put another way, if the total modulo 10 is equal to 0), then the number

* is valid according to the Luhn formula; else it is not valid.

*

* As an illustration, if the account number is 49927398716, it will be validated as follows:

* i. Double every second digit, from the rightmost:

* (1×2) = 2, (8×2) = 16, (3×2) = 6, (2×2) = 4, (9×2) = 18

* ii. Sum all the individual digits (digits in parentheses are the products from Step 1):

* 6 + (2) + 7 + (1+6) + 9 + (6) + 7 + (4) + 9 + (1+8) + 4 = 70

* iii. Take the sum modulo 10: 70 mod 10 = 0; the account number is valid.

* @param num

* @return boolean true-valid; false-invalid

public static boolean isValidCC(String num) {

// //Check digits

// if(!num.matches("^\\d{13,19}$"))

// return false;

//Check mod10

final int[][] sumTable = {{0,1,2,3,4,5,6,7,8,9},{0,2,4,6,8,1,3,5,7,9}};

int sum = 0, flip = 0;

for (int i = num.length() - 1; i >= 0; i--, flip++){

int n = num.charAt(i) - '0';

if (n < 0 || n > 9)

return false;

sum += sumTable[flip & 0x1][n];

}

return (sum == 0) ? false : (sum % 10 == 0);

}

/**

* Check whether a credit card number is valid or not according to the Luhn algorithm (MOD10).

* Used switch to double specified value.

* @param number

* @return

public static boolean isValidCC1(String number) {

int sum = 0;

int mul = 1;

for (int i = number.length() - 1; i >= 0; i--) {

int n = number.charAt(i) - '0';

if (n < 0 || n > 9)

return false;

n *= (mul == 1) ? mul++ : mul--;

sum += (n>9 ? n-9 : n);

}

return (sum == 0) ? false : (sum % 10 == 0);

}

/**

* Check whether a credit card number is valid or not according to the Luhn algorithm (MOD10).

* Used position to double specified value.

* @param number

* @return

public static boolean isValidCC2(String number) {

int sum = 0;

for (int i = number.length() - 1; i >= 0; i--) {

int n = number.charAt(i) - '0';

if (n < 0 || n > 9)

return false;

if ((number.length()-i)%2 == 0)

n *= 2;

sum += (n>9 ? n-9 : n);

}

return (sum == 0) ? false : (sum % 10 == 0);

}

/**

* Check whether a credit card number is valid or not according to the Luhn algorithm (MOD10).

* Used AND and XOR to double specified value.

* @param number

* @return

public static boolean isValidCC3(String number) {

int digits = number.length();

int oddOrEven = digits & 1;

long sum = 0;

for (int i = 0; i < digits; i++) {

int n = number.charAt(i) - '0';

if (n < 0 || n > 9)

return false;

if (((i & 1) ^ oddOrEven) == 0)

n *= 2;

sum += (n>9 ? n-9 : n);

}

return (sum == 0) ? false : (sum % 10 == 0);

}

/**

* Check whether a credit card number is valid or not according to the Luhn algorithm (MOD10).

* Used a variable as switch to double specified value.

* @param number

* @return

private static boolean isValidCC4(String number) {

int sum = 0;

boolean alternate = false;

for (int i = number.length() - 1; i >= 0; i--) {

int n = Integer.parseInt(number.substring(i, i + 1)); //May throw out a runtime exception

if (n < 0 || n > 9)

return false;

if (alternate)

n *= 2;

sum += (n>9 ? n%10 + 1 : n);

alternate = !alternate;

}

return (sum == 0) ? false : (sum % 10 == 0);

}

信用卡前缀及校验规则

CARD TYPE	Prefix	Length	Check digit algorithm
MASTERCARD	51-55	16	mod 10
VISA	4	13, 16	mod 10
AMEX	34 37	15	mod 10
Diners Club/ Carte Blanche	300-305 36 38	14	mod 10
Discover	6011	16	mod 10
enRoute	2014 2149	15	any
JCB	3	16	mod 10
JCB	2131 1800	15	mod 10

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