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I'm trying to calculate any ISBN-13 Number's Check Digit, I'm not too worried if the ISBN number is valid or invalid, but what I've been trying to do is get the code to work. There are obviously flaws in my interpretation of the algorithm, suggestions on how to fix it are welcome but the primary problem is receiving user input that is too large for an integer variable but I also want to avoid the decimals of the double value.

I already tried to use the BigDecimal and BigNumber but I simply don't have enough experience to be able to understand them completely. This is the algorithm to find d13 (the Check Digit): 10-(d1 +3d2 +d3 +3d4 +d5 +3d6 +d7 +3d8 +d9 +3d10 +d11 +3d12)%10.

The Code is a mess I know. I've used this website as a reference to what I want to do and I've been using this ISBN number as my practice: 9780132130806.

Again my question is how can I print the final ISBN number without decimals and how can I possibly fix my algorithm? (I'd also really appreciate any tips on a website that helps with teaching JOption as that is the prefered method i use because it looks a bit cleaner to me than using the scanner)

import javax.swing.JOptionPane;
import java.math.BigInteger;

public class ISBN
{
    //George Sayegh Calculate check Digit ISBN

    public static void main(String[] args)
    {
    //Define Variables
    double ISBN12, D1, D2, D3, D4, D5, D6, D7, D8, D9, D10, D11, D12 = 0, D13;
    double A = 100000000000L;
    double B = 10000000000L;
    double C = 1000000000;
    double D = 100000000;
    double E = 10000000;
    double F = 1000000;
    double G = 100000;
    double H = 10000;
    double I = 1000;
    double J = 100;
    double K = 10;
    double L = 1;

    //Get ISBN #
    String ISBN12text = JOptionPane.showInputDialog("Please enter the first 12 digits of your ISBN number");
    ISBN12 = Double.parseDouble(ISBN12text);

    //Calculate D1
    D1 = ((ISBN12 - (ISBN12 % A)) / A); 

    //Calculate D2
    D2 = ((ISBN12 - (ISBN12 % B)) / B);

    //Calculate D3
    D3 = ((ISBN12 - (ISBN12 % C)) / C);

    //Calculate D4
    D4 = ((ISBN12 - (ISBN12 % D)) / D);

    //Calculate D5
    D5 = ((ISBN12 - (ISBN12 % E)) / E);

    //Calculate D6
    D6 = ((ISBN12 - (ISBN12 % F)) / F);

    //Calculate D7
    D7 = ((ISBN12 - (ISBN12 % G)) / G);

    //Calculate D8
    D8 = ((ISBN12 - (ISBN12 % H)) / H);

    //Calculate D9
    D9 = ((ISBN12 - (ISBN12 % I)) / J);

    //Calculate D10
    D10 = ((ISBN12 - (ISBN12 % K)) / K);

    //Calculate D11
    D11 = ((ISBN12 - (ISBN12 % L)) / L);

    //Get D13
    D13 = 10 - (D1 + (3 * D2) + D3 + 3 * D4 + D5 + 3 * D6 + D7 + 3 * D8 + D9 + 3 * 10 + D11 + 3 * D12) % 10; 

    JOptionPane.showMessageDialog(null, D1 +""+ D2 +""+ D3 +""+ D4 +""+ D5 +""+ D6 +""+ D7 +""+ D8 +""+ D9 +""+ D10 +""+ D11 +""+ D12 +""+ 13);
    }
}
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2 回答 2

2

这是基于此 Wikipedia 示例的更简单的实现。它缺乏健全性检查——例如输入字符串是否是有效的 ISBN13——但应该足以让你继续前进。我希望它有所帮助。

请注意，输入是一个 ISBN-13 字符串，其中已删除校验位（例如 978013213080，而不是 9780132130806）；程序在输出上打印校验位；如果这不是您想要的，您应该可以修改它。

public class CheckISBN13 {
    /* We assume isbnString is a *valid* ISBN-13 with the check digit removed.  */
    public static int[] stringToInt(String isbnString) {
        int[] isbnInt = new int[12];
        int j = 0;
        for (int i = 0; i < isbnString.length(); ++i) {
            if (Character.isDigit(isbnString.charAt(i))) {
                isbnInt[j++] = Character.getNumericValue(isbnString.charAt(i));
            }
        }
        return isbnInt;
    }

    public static int getCheckDigit(int[] isbnInt) {
        int val = 0;
        for (int i = 0; i < isbnInt.length; ++i) {
            int coeff = (i % 2 == 0 ? 1 : 3);
            val += coeff * isbnInt[i];
        }
        return 10 - (val % 10);
    }

    public static void main(String[] args) {
        if (args.length < 1) {
            System.err.println("Usage: java CheckISBN13 978-0-306-40615");
            System.exit(-1);
        }
        String isbnString = args[0];
        int[] isbnInt = stringToInt(isbnString);
        System.out.println("Check digit: " + getCheckDigit(isbnInt));
    }
}
于 2016-03-05T11:25:15.127 回答
2

试试这个极其简单的算法（用 Python 编写，但转换成 Java 应该很容易）。希望这些评论足以解释。应转换为不超过 10 行（为了便于阅读，不包括空行）

#// Valid ISBN-12 string from user (12 numbers, doesn't matter what other characters)
isbn12 = '978-0-306-40615' #// Input it from the user, hardcoded Wikipedia example for testing
coeff = 1 #// Multiple used in calculating sum
sum = 0

for d in isbn12: #// Equivalent to for(char d : isbn12.toCharArray())
    #// this next block is just a tryParse or an isDigit check
    #// if the character is a digit, parse it to an int
    #// else continue to next iteration
    try:
        #// just reassigning the value because-
        #// Hey, this is Python!
        d = int(d)
    except ValueError:
        continue

    #// Add to sum after multiplying with coeff
    sum += d * coeff
    #// If coeff was 1, change to 3 and vice versa
    #// Equivalent to coeff == 1 ? 3 : 1 in Java
    coeff = 3 if coeff == 1 else 1

#// END FOR LOOP

#// Get positive number to be added to make ISBN divisible by 10
#// The extra % 10 at the end is for changing 10 to 0 without if
check_digit = (10 - sum % 10) % 10

//（每条评论开头的额外是为了让SO代码格式化认为是评论）

于 2016-03-05T11:52:38.560 回答