我尝试使用Luhn算法检查信用卡的验证,该算法的工作原理如下:
从右到左加倍每秒.如果数字加倍会产生两位数字,请将两位数相加以得到一位数字.
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
现在添加步骤1中的所有单位数字.
4 + 4 + 8 + 2 + 3 + 1 + 7 + 8 = 37
在卡号中从右到左添加奇数位的所有数字.
6 + 6 + 0 + 8 + 0 + 7 + 8 + 3 = 38
对步骤2和步骤3的结果求和.
37 + 38 = 75
如果步骤4的结果可被10整除,则卡号有效; 否则,它无效.例如,号码4388576018402626无效,但号码4388576018410707有效.
简单地说,我的程序始终显示对我输入的所有内容都有效.即使它是有效数字,sumOfOddPlace和sumOfDoubleEvenPlace方法的结果也等于零.
任何帮助表示赞赏.
import java.util.Scanner; public class CreditCardValidation { public static void main(String[] args) { Scanner in = new Scanner(System.in); int count = 0; long array[] = new long [16]; do { count = 0; array = new long [16]; System.out.print("Enter your Credit Card Number : "); long number = in.nextLong(); for (int i = 0; number != 0; i++) { array[i] = number % 10; number = number / 10; count++; } } while(count < 13); if ((array[count - 1] == 4) || (array[count - 1] == 5) || (array[count - 1] == 3 && array[count - 2] == 7)){ if (isValid(array) == true) { System.out.println("\n The Credit Card Number is Valid. "); } else { System.out.println("\n The Credit Card Number is Invalid. "); } } else{ System.out.println("\n The Credit Card Number is Invalid. "); } } public static boolean isValid(long[] array) { int total = sumOfDoubleEvenPlace(array) + sumOfOddPlace(array); if ((total % 10 == 0)) { for (int i=0; i< array.length; i++){ System.out.println(array[i]);} return true; } else { for (int i=0; i< array.length; i++){ System.out.println(array[i]);} return false; } } public static int getDigit(int number) { if (number <= 9) { return number; } else { int firstDigit = number % 10; int secondDigit = (int) (number / 10); return firstDigit + secondDigit; } } public static int sumOfOddPlace(long[] array) { int result = 0; for (int i=0; i< array.length; i++) { while (array[i] > 0) { result += (int) (array[i] % 10); array[i] = array[i] / 100; }} System.out.println("\n The sum of odd place is " + result); return result; } public static int sumOfDoubleEvenPlace(long[] array) { int result = 0; long temp = 0; for (int i=0; i< array.length; i++){ while (array[i] > 0) { temp = array[i] % 100; result += getDigit((int) (temp / 10) * 2); array[i] = array[i] / 100; } } System.out.println("\n The sum of double even place is " + result); return result; } }
Nicholas Ng.. 24
您可以自由导入以下代码:
public class Luhn { public static boolean Check(String ccNumber) { int sum = 0; boolean alternate = false; for (int i = ccNumber.length() - 1; i >= 0; i--) { int n = Integer.parseInt(ccNumber.substring(i, i + 1)); if (alternate) { n *= 2; if (n > 9) { n = (n % 10) + 1; } } sum += n; alternate = !alternate; } return (sum % 10 == 0); } }
链接参考:https://github.com/jduke32/gnuc-credit-card-checker/blob/master/CCCheckerPro/src/com/gnuc/java/ccc/Luhn.java
谷歌和维基百科是你的朋友.我将使用int-array而不是long-array.在Wikipedia上发布以下java代码(以及Luhn算法的详细说明):
public static boolean check(int[] digits) { int sum = 0; int length = digits.length; for (int i = 0; i < length; i++) { // get digits in reverse order int digit = digits[length - i - 1]; // every 2nd number multiply with 2 if (i % 2 == 1) { digit *= 2; } sum += digit > 9 ? digit - 9 : digit; } return sum % 10 == 0; }
您应该处理输入处理代码.我建议你研究以下解决方案:
public static void main(String[] args) { Scanner in = new Scanner(System.in); boolean repeat; List<Integer> digits = new ArrayList<Integer>(); do { repeat = false; System.out.print("Enter your Credit Card Number : "); String input = in.next(); for (int i = 0; i < input.length(); i++) { char c = input.charAt(i); if (c < '0' || c > '9') { repeat = true; digits.clear(); break; } else { digits.add(Integer.valueOf(c - '0')); } } } while (repeat); int[] array = new int[digits.size()]; for (int i = 0; i < array.length; i++) { array[i] = Integer.valueOf(digits.get(i)); } boolean valid = check(array); System.out.println("Valid: " + valid); }
您可以自由导入以下代码:
public class Luhn { public static boolean Check(String ccNumber) { int sum = 0; boolean alternate = false; for (int i = ccNumber.length() - 1; i >= 0; i--) { int n = Integer.parseInt(ccNumber.substring(i, i + 1)); if (alternate) { n *= 2; if (n > 9) { n = (n % 10) + 1; } } sum += n; alternate = !alternate; } return (sum % 10 == 0); } }
链接参考:https://github.com/jduke32/gnuc-credit-card-checker/blob/master/CCCheckerPro/src/com/gnuc/java/ccc/Luhn.java