import java.util.Scanner;

public class Chapter3_9 {
    public static void main(String[] args) {
        int isbn, checkSum;
        int d1, d2, d3, d4, d5, d6, d7, d8, d9;

        System.out.println("Enter the first 9 digits of an ISBN as integer: ");
        Scanner input = new Scanner(System.in);
        isbn = input.nextInt();

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

        checkSum = (d1 * 1 + d2 * 2 + d3 * 3 + d4 * 4 + d5 * 5 + d6 * 6 + d7 * 7 + d8 * 8 + d9 * 9) % 11;
        if (checkSum == 10)
            System.out.println("The ISBN-10 number is " + d1 + d2 + d3 + d4 + d5 + d6 + d7 + d8 + d9 + "X");
        else
            System.out.println("The ISBN-10 number is " + d1 + d2 + d3 + d4 + d5 + d6 + d7 + d8 + d9 + checkSum);
        System.exit(1);
    }
}

"C:\Program Files\Java\jdk1.8.0_241\bin\java.exe" "-javaagent:C:\Users\86152\Desktop\IntelliJ IDEA 2020.2\lib\idea_rt.jar=65409:C:\Users\86152\Desktop\IntelliJ IDEA 2020.2\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.8.0_241\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\rt.jar;C:\Users\86152\IdeaProjects\untitled\out\production\untitled" Chapter3_9
Enter the first 9 digits of an ISBN as integer: 
013031997
The ISBN-10 number is 013031997X

Process finished with exit code 1
 

import java.util.Scanner;
public class Chapter3_10 {
    public static void main(String[] args) {
        int number1 = (int)(Math.random() * 100);
        int number2 = (int)(Math.random() * 100);

        Scanner input = new Scanner(System.in);
        System.out.println("What is " + number1 + " + " + number2 + " ？");
        int answer = input.nextInt();

        if (number1 + number2 == answer)
            System.out.println("Your are correct!");
        else{
            System.out.println("Your answer is wrong.");
            System.out.println(number1 + " + " + number2 + " should be " + (number1 + number2));

        }
        input.close();

    }
}

"C:\Program Files\Java\jdk1.8.0_241\bin\java.exe" "-javaagent:C:\Users\86152\Desktop\IntelliJ IDEA 2020.2\lib\idea_rt.jar=65471:C:\Users\86152\Desktop\IntelliJ IDEA 2020.2\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.8.0_241\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_241\jre\lib\rt.jar;C:\Users\86152\IdeaProjects\untitled\out\production\untitled" Chapter3_10
What is 0 + 31 ？
35
Your answer is wrong.
0 + 31 should be 31

Process finished with exit code 0