Question

我正在研究信用卡号验证应用程序。

我可以输入有效数字或无效数字，但是输出从不接受数据并将其读取为有效数据。我正在尝试找出正确的信用卡验证算法。

下面是我想要的结果。我需要知道循环的哪一点，或者我弄乱了long vs. string的用法，这会导致输出始终显示为无效。

示例1：

Enter a credit card number: 4246345689049834

4246345689049834 is invalid

示例2：

Enter a credit card number: 4388576018410707

4388576018410707 is valid

但是，在我的代码中，我得到了以下输出

示例1：

Enter a credit card number: 4246345689049834

4246345689049834 is invalid

示例2：

Enter a credit card number: 4388576018410707

4388576018410707 is invalid

代码：

    public static void main(String args[]) {
        Scanner input = new Scanner(System.in);

        System.out.println("Enter Credit Card Number for Validation: ");
        long number = input.nextLong();

        long total = sumOfEvenPlaces(number) + sumOfOddPlaces(number);

        if (isValid(total)) {
            System.out.println(number + " is valid");
        } else {
            System.out.println(number + " is invalid");
        }
    }

    public static boolean isValid(long total) {
        if (total % 10 == 0) {
            return true;
        }
        return false;
    }

    public static int sumOfEvenPlaces(long number) {
        int sum = 0;
        int remainder;
        number %= 10;
        while (number % 10 != 0 || number / 10 != 0) {
            remainder = (int) (number % 10);

            sum = sum + getDigit(remainder * 2);
            number /= 100;
        }
        return sum;
    }

    public static int getDigit(int number) {
        if (number > 9) {
            return (number % 10 + number / 10);
        }
        return number;
    }

    public static int sumOfOddPlaces(long number) {
        int sum = 0;
        int remainder;

        while (number % 10 != 0 || number / 10 != 0) {
            remainder = (int) (number % 10);
            sum = sum + getDigit(remainder);
            number /= 100;
        }
        return sum;
    }
}

Answer 1

您在sumOfEvenPlaces()和sumOfOddPlaces()方法中都犯了错误。

在sumOfEvenPlaces(long number)中，您必须进行更改

 number %= 10;

到

 number /= 10;

您只能使用数字/ 10跳过数字，而不能跳过数字％10

在两个函数中都更改

 while (number % 10 != 0 || number / 10 != 0)

到

 while (number > 0)

使用while（数字> 0）循环将一直运行，直到处理完数字中的所有数字为止。

尝试这些修改后的方法，它将起作用：-

public static int sumOfEvenPlaces(long number) {
    int sum = 0;
    int remainder;
    number /= 10;          // change 1
    while (number > 0) {   // change 2
        remainder = (int) (number % 10);
        sum = sum + getDigit(remainder * 2);
        number /= 100;
    }
    return sum;
}

public static int sumOfOddPlaces(long number) {
    int sum = 0;
    int remainder;

    while (number > 0) {   // change 3 
        remainder = (int) (number % 10);
        sum = sum + getDigit(remainder);
        number /= 100;
    }
    return sum;
}

输出：-

Enter Credit Card Number for Validation: 
 4246345689049834
4246345689049834 is invalid

信用卡长/字符串验证

1 个答案: