custom made exception

Question

I did a custom made exception but I am not sure if it is correct and also I don't know why is a case of an exception the program is not printing the message for the exception but only the name of the class for the custom exception, and also how can I make it in a case of an exception to terminate the program because in the moment the program only informs about the exceptions and go on. The program is compiling and running on eclipse. Cheers guys. Here is the code.

import java.util.Scanner;
public class Stud
{
    public static void main(String[] args)
    {
        Scanner input = new Scanner(System.in);

        System.out.println("Enter age of the student");
        int age = input.nextInt();
        try
        {
                if(age < 7 || age > 18)
                {   
                    throw new InvalidStudentException("Age can't be less than 7 and more than 18");
                }
        }
        catch(InvalidStudentException e)
        {
                System.err.println(e) ;
        }

        System.out.println("Enter the gender of the student");
        String gender = input.next();
        try
        {
            if((!gender.equals("male")) || (!gender.equals("female")))
            {
                throw new InvalidStudentException("Gender can be only male or female");
            }
        }catch(InvalidStudentException e)
        {
            System.err.println(e) ;
        }

        System.out.println("Enter the name of the student");
        String name = input.next();
        try
        {


            if(name.length() < 10 || name.length() > 50)
            {
                throw new InvalidStudentException("The length of the name must be greater than 10 and less than 50 characters");
            }
        }catch(InvalidStudentException e)
        {
            System.err.println(e) ;
        }

        System.out.println("Enter the class number for the student");
        int classNumber = input.nextInt();

        try
        {
            if(classNumber < 1 || classNumber > 11)
            {
                throw new InvalidStudentException("Class number can be only between 1 and 11");
            }
        }catch(InvalidStudentException e)
        {
            System.err.println(e) ;
        }
    }
}

/** the class with the custom made exception
 */
public class InvalidStudentException extends Exception
{
    String msg;
    int num;

     public InvalidStudentException() 
     {
         super();
     }

     public InvalidStudentException(String msg) 
     {
         super();
         this.msg = msg;
     }
     public InvalidStudentException(int num) 
     {
         super();
         this.num = num;
     }
}

Surender Thakran · Accepted Answer · 2012-06-14 05:49:54Z

2

you need to raise an exception if the gender is not male and neither female, so change your code to this:

try
    {
        if((!gender.equals("male")) && (!gender.equals("female")))
        {
            throw new InvalidStudentException("Gender can be only male or female");
        }
    }catch(InvalidStudentException e)
    {
        System.err.println(e.getMessage()) ;
        System.exit(0);
    }

note && instead of ||

answered Jun 14, 2012 at 5:49

Surender Thakran

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Comments

Basit Anwer · Accepted Answer · 2012-06-14 05:53:07Z

2

In your Exception class override the toString() method

@Override
 public String toString()
 {
     return this.msg.toString();
 }

to print the stack trace is another question.

answered Jun 14, 2012 at 5:53

Basit Anwer

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Comments

Jigar Joshi · Accepted Answer · 2012-06-14 05:43:30Z

1

You are catching the exception so the program will move on in exceptional cases too. You could rethrow using throw it from catch block or use System.exit()

To print the details of exception

use

e.printStackTrace()

instead of System.out.println(e);

Also See

Catching and Handling Exceptions

edited Jun 14, 2012 at 5:43

answered Jun 14, 2012 at 5:36

Jigar Joshi

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2 Comments

Kiril Over a year ago

alright and do you know how to make the exception message to be the one in the InvalidStudentException("Age can't be less than 7 and more than 18"); instead showing only the name of the class itself

Jigar Joshi Over a year ago

if you just need the exception message then use e.getMessage()

MaVRoSCy · Accepted Answer · 2012-06-14 05:38:58Z

1

try this

    try
    {
        if((!gender.equals("male")) || (!gender.equals("female")))
        {
            throw new InvalidStudentException("Gender can be only male or female");
        }
    }catch(InvalidStudentException e)
    {
        System.err.println(e.getMessage()) ;
        System.exit(0);
    }

answered Jun 14, 2012 at 5:38

MaVRoSCy

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