A question about the bank card number rules, according to the rules for bank card verification

Currently, the first six digits of the current 16-digit UnionPay card number are 622126 ~ Between 622925, 7 to 15 digits are customized by the bank,
It may be a card issuing branch, card issuing outlet, card issuing number, and 16th bits are verification codes.

The 16-bit card number verification bit is calculated using the luhm verification method:

1. Numbers 1 to 15 of the 15-digit card numbers without verification digits are numbered from right to 15, and the numbers on the odd-digit number are multiplied by 2.
2. Add all the ten digits of the odd-bits product and all the numbers on the even-bits.
3. The addition and addition of the check bit can be divided by 10.

For example, the card number:

6 2 2 5 8 8 1 4 4 2 0 7 4 3*2 2 2 2 2 2 2 2 ------------------------------------------------------ 12 2 4 5 16 8 2 4 2 4 4 14 4 6 will the preceding number addition: 1 + 2 + 2 + 4 + 5 + 1 + 6 + 8 + 2 + 4 + 2 + 4 + 4 + 1 + 4 + 4 + 6 = 60 due to 60 + 0 divided by 10, therefore, the checkpoint is 0, so the card number is 6225 8814 1420.

If one of the digits is replaced, the last check bit is incorrect.

I wrote a program for computation:

Public class test5 {public static void main (string [] ARGs) {string card = "622588141420743"; system. out. println ("card:" + card); system. out. println ("Check Code:" + getbankcardcheckcode (card); system. out. println ("card ID:" + card + getbankcardcheckcode (card ));} /*** verify the bank card number * @ Param cardid * @ return */public static Boolean checkbankcard (string cardid) {char bit = getbankcardcheckcode (Car Did. substring (0, cardid. length ()-1); Return cardid. charat (cardid. length ()-1) = bit ;} /*** obtain the checkpoint from the bank card number without the checkpoint using the luhm Verification Algorithm * @ Param noncheckcodecardid * @ return */public static char getbankcardcheckcode (string noncheckcodecardid) {If (noncheckcodecardid = NULL | noncheckcodecardid. trim (). length () = 0 |! Noncheckcodecardid. Matches ("// D +") {Throw new illegalargumentexception ("bank card code must be number! ");} Char [] CHS = noncheckcodecardid. trim (). tochararray (); int luhmsum = 0; For (INT I = chs. length-1, j = 0; I> = 0; I --, J ++) {int K = CHS [I]-'0 '; if (J % 2 = 0) {K * = 2; k = K/10 + K % 10;} luhmsum + = K ;} return (luhmsum % 10 = 0 )? '0': (char) (10-luhmsum % 10) + '0 ');}}