第三章第九题（商业：检验ISBN-10）((Business: check ISBN-10))_( 商 业 : 检 查 isbn-10 ) isbn-10 ( 国 际标准书号 )以前是一个 10

第三章第九题（商业：检验ISBN-10）((Business: check ISBN-10))

• **3.9（商业：检验ISBN-10）ISBN-10（国际标准书号）由10个个位整数d1d2d3d4d5d6d7d8d9d10组成，最后一位d10是校验和，它是使用下面的公式用另外9个数计算出来的：
  (d1 * 1 + d2 * 2 + d3 * 3 + d4 * 4 + d5 * 5 + d6 * 6 + d7 * 7 + d8 * 8 + d9 * 9)%11
  如果校验和为10，那么按照ISBN-10的习惯，最后一位应该表示为X。编写程序，提示用户输入前9个数，然后显示10位ISBN（包括前面起始位置的0）。程序应该读取一个整数输入。
  以下是一个运行示例：

  Enter the first 9 digits of an ISBN as integer:013601267

  The ISBN-10 number is 0136012671

  Enter the first 9 digits of an ISBN as integer:013031997

  The ISBN-10 number is 013031997X

  **3.9(Business: check ISBN-10) An ISBN-10 (International Standard Book Number) consists of 10 digits: d1d2d3d4d5d6d7d8d9d10. The last digit, d10, is a checksum, which is calculated from the other 9 digits using the following formula:
  (d1 * 1 + d2 * 2 + d3 * 3 + d4 * 4 + d5 * 5 + d6 * 6 + d7 * 7 + d8 * 8 + d9 * 9)%11
  If the checksum is 10, the last digit is denoted as X according to the ISBN-10 convention. Write a program that prompts the user to enter the first 9 digits and displays the 10-digit ISBN (including leading zeros). Your program should read the input as an integer.
  Here are sample runs:

  Enter the first 9 digits of an ISBN as integer:013601267

  The ISBN-10 number is 0136012671

  Enter the first 9 digits of an ISBN as integer:013031997

  The ISBN-10 number is 013031997X

• 参考代码：

package chapter03;

public class Code_09 {
    public static void main(String[] args){

        java.util.Scanner input = new java.util.Scanner(System.in);

        System.out.print("Enter the first 9 digits of an ISBN as integer: ");
        int first9Digits = input.nextInt();

        int d9 = first9Digits %10;
        int d8 = first9Digits /10 % 10;
        int d7 = first9Digits /100 % 10;
        int d6 = first9Digits /1000 % 10;
        int d5 = first9Digits /10000 % 10;
        int d4 = first9Digits /100000 % 10;
        int d3 = first9Digits /1000000 % 10;
        int d2 = first9Digits /10000000 % 10;
        int d1 = first9Digits /100000000;

        int d10 = (int)((d1 *1 + d2 * 2 + d3 * 3 + d4 * 4 + d5 * 5 + d6 * 6 + d7 * 7 + d8 * 8 + d9 * 9)%11);

        if(d10 == 10)
            System.out.println("The ISBN-10 number is " +first9Digits+"X");
        else
            System.out.println("The ISBN-10 number is " +first9Digits+d10);

    }
}

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• 结果显示：

Enter the first 9 digits of an ISBN as integer: 013601267
The ISBN-10 number is 136012671

Process finished with exit code 0

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