java – 使用Luhn算法检查信用卡有效性

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
>总结步骤2和步骤3的结果.

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;
    }
     }

解决方法:

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

标签：java,arrays,validation,credit-card,luhn
来源： https://codeday.me/bug/20190926/1818127.html