Question

*In Java please!

EXCEPTION HANDLING
Concept Summary:
1. Exception   handling  
2. Class   design

Description
Write   a   program   that   creates   an   exception   class   called   ManyCharactersException,   designed  
to   be   thrown   when   a   string   is   discovered   that   has   too   many   characters   in   it.
Consider   a   program   that   takes   in   the   last   names   of   users.   The   driver   class   of   the   program
reads the   names   (strings) from   the   user   until   the   user   enters   "DONE".   If   a   name is   entered  
that   has   more   than   20   characters,   throw   the   exception.  
Design   the   program   such   that   it   catches   and   handles   the   exception   if   it   is   thrown.   Handle  
the   exception   by   printing   an   appropriate   message,   and   then   continue   processing   more  
names by   getting   more   inputs   from   the   user. Note:   Your   program   should   exit   only   when   the  
user   enters   "DONE".

SAMPLE OUTPUT:
Enter strings. When finished enter DONE
Short string
You entered: Short string
Medium size string
You entered: Medium size string
Really really long string, someone stop me!
You entered too many characters
DONE
You entered: DONE
Good bye!
RUBRICS:
Design   the   Exception class   (20   points):
Constructing   the   Try…   Catch…   Throw within   the   Driver   class   (40   points)
Constructing   Error   Message   for   the   Exception   class   (10   points)
Constructing   other   error   messages   (20   points)
Loop   and   other   constructs   to   complete   the   program   (10   points)

Answer 1

Solution - Required code has been provided below along with the output. Comments have been placed in the code to depict the functionality of the various statements/functions.

There is an exception class defined, in which the constructor has been defined to print the required error message when the string length is too long. Code runs until user enters "DONE" (all in caps)

Code

import java.util.*;

//Except class 
class ManyCharactersException extends Exception 
{

        //Definded Constructor to print error when exception is thrown
 ManyCharactersException(String s)
 {
        System.out.println(s);
 }

}


public class ExceptionTest {

        public static void main (String args[])
        {
                //Scanner to read user input
                Scanner reader = new Scanner(System.in);

                //input from user with a loop 
                System.out.println("Enter strings. When finished enter DONE");
                String s = reader.nextLine();

                while (s.equals("DONE") == false)
                {
                        try 
                        {
                                if (s.length() > 20)
                                {
                                        //throw the exception with the message
                                        throw new ManyCharactersException("You entered too many characters");                           
                                }
                                else 
                                {
                                        System.out.println("You entered: "+s);
                                        s= reader.nextLine();
                                }
                        }
                        catch(ManyCharactersException exp)
                        {
                                s= reader.nextLine();
                        }
                }
                System.out.println("You entered: "+s);
                System.out.println("Good bye!");

        }
}

Output: user input has been shown in purple colour.

java ExceptionTest
Enter strings. When finished enter DONE
Short string
You entered: Short string
medium string
You entered: medium string
very very very long string
You entered too many characters
DONE
You entered: DONE
Good bye!