Question

You are to write a program (BookExceptionsDemo.java) that will create and, using user input, populate an array of instances of the class Book. The class Book is loaded in our Canvas files: Book.java

• The user will enter a number n (n must be > 0, trap the user until they input a valid value for n), Your program will declare and create an array of size n of instances of the class Book.
• The user will be asked to enter the information for each instance that is to be created. The following exceptions will be thrown if the user enters information that is not appropriate to the request:
• InputMismatchException: Thrown if the user enters a non-matching type. Trap the user until they enter a valid value.
• PagesException: Thrown if the user enters a number <=0 for the number of pages. Trap the user until they enter a valid value.
• CostException: Thrown if the user enters a number < 0 for the cost of the book. Trap the user until they enter a valid value.
• CategoryException: Thrown if the user enters a value other than "Fiction", “Non-Fiction", "Reference", or “Text" for the category of the book. Trap the user until they enter a valid value.
• You are to create the classes PageException,.java, CostException.java and CategoryException.java (children of the class Exception). The string stored in the instance variable message of the respective exception classes should indicate which exception was thrown. InputMismatchException is a class of the Java language, see the Java API for more information.
• Upon entrance of acceptable information the gathered information will be the arguments passed to the non-default constructor, of the Book class, the instance created will be saved in the array of instances of the class Book.

Name your program BookExceptionsDemo_yourInitials..java, where yourInitials represents your initials and send all programs developed for this assignment (including Book.java). It would be helpful if you could put those files in a zip file (name that zip file BookExceptions_yourInitials.zip, where yourInitials represents your initials).

Answer 1

Summary :

Following files are pasted below and Demo output is shown towards end as 2 exhibits.

BookExceptionDemo.java

Book.java

PagesException.java

CostException.java

CategoryException.java

InputMismatchException.java

############################### BookExceptionDemo.java ####################

import java.io.RandomAccessFile;
import java.util.Scanner;
import java.util.ListIterator;
import java.util.*;
import java.io.*;
import lib.PagesException;
import lib.InputMismatchException;
import lib.CategoryException;
import lib.CostException;

import lib.Book;

public class BookExceptionsDemo {
   Scanner in ;
   int num_books ;
   Book[] book_list ;
   boolean flag ;
  
   public BookExceptionsDemo() {
        in = new Scanner(System.in);
       num_books = -1;
       this.flag = false ;
   }
  
   public boolean getFlag() {
       return this.flag ;
   }
  
   public void resetFlag() {
       this.flag = false ;
   }
  
   public void setFlag() {
       this.flag = true ;
   }
   // Read num of books
   public void readNumBooks() throws InputMismatchException {

       System.out.println("Enter number of Books : ");
       int input = in.nextInt(); in.nextLine();
       if ( input > 0 ) {
           this.num_books = input ;
       } else {
           throw new InputMismatchException();
       }
  
   }
   // Read Pages input
   public int readPages() throws PagesException {

       System.out.println("Enter Pages : ");
       int input = in.nextInt();in.nextLine();
       if ( input > 0 ) {
           return input;
       } else {
           throw new PagesException();
       }
  
   }
  
   // Read Cost Input
   public int readCost() throws CostException {

       System.out.println("Enter Cost : ");
       int input = in.nextInt();in.nextLine();
       if ( input >= 0 ) {
           return input;
       } else {
           throw new CostException();
       }
  
   }
  
   // Read Category Input
   public String readCategory() throws CategoryException {

       System.out.println("Enter Category of Books : ");
       String input = in.nextLine();
       if ( ("Fiction".equals(input) ) || ("Non-Fiction".equals(input)) || ("Reference".equals(input) ) || ("Text".equals(input))) {
           return input ;
       } else {
           throw new CategoryException();
       }
  
   }
  
  
    public static void main(String[] args) {
       // Flag to loop while invalid inputs
       boolean input_received = false ;
       // Values to store temp Book parameters
       int cost =0 , pages =0 ;
       String category = " "       ;
      
       BookExceptionsDemo be = new BookExceptionsDemo() ;
      
           // Read Num of Books till valid
       while( !input_received) {
           try {
               be.readNumBooks();
               input_received = true ;
           } catch (InputMismatchException e ) {
                   System.out.println(" Invalid Number of books : " );
                   e.getMesg();
                  
           }
          
       }
       // Create Num_Books array of Book
       be.book_list = new Book[be.num_books];
      
       // Loop thru num_books reading pages cost and category
       for ( int i = 0 ; i < be.num_books ; i ++ ) {
           input_received = false ;
           while ( ! input_received ) {
               try {
                   pages = be.readPages();
                   input_received = true;
               } catch ( Exception e ) {
                   System.out.println(" Invalid Pages " );
                              
               }
           }

           input_received = false ;
           while ( ! input_received ) {
               try {
                   cost = be.readCost();
                   input_received = true;
               } catch ( Exception e ) {
                   System.out.println(" Invalid Cost " );
                              
               }
           }          
          
          
          
           input_received = false ;
           while ( ! input_received ) {
               try {
                   category = be.readCategory();
                   input_received = true;
               } catch ( Exception e ) {
                   System.out.println(" Invalid Category " );
                              
               }
           }

           // Create Book and insert into Array .
           be.book_list[i] = new Book(pages,cost , category);
          
       }

       // Display ALl the Books .
       for (int j = 0 ; j < be.num_books ; j++ ) {
          
           be.book_list[j].display();
       }

   }

}

############################### End BookExceptionDemo.java ####################

############################### Book.java ####################

package lib;
public class Book {

   private int pages ;
   private int cost ;
   private String category ;

   public Book() {
       this.pages = 0 ;
       this.cost = 0;
       this.category = " " ;
   }

   public Book( int ppages , int pcost , String pcategory ) {
       this.pages = ppages ;
       this.cost = pcost;
       this.category = pcategory ;
   }

   public void display() {
       System.out.println( " Category : " + category + " Pages : " + pages + " Cost : " + cost );
   }

}  

############################### End Book.java ####################

############################### PagesException.java ####################

package lib;

public class PagesException extends Exception {

   public PagesException() {
        super("Pages value Invalid \n");
   }  

   public String getMesg() {
       return "Pages value Invalid";
   }

}

############################### End PagesException.java ####################

############################### CostException.java ####################

package lib;

public class CostException extends Exception {

   public CostException() {
        super("Cost value Invalid \n");
   }  

   public String getMesg() {
       return "Cost value Invalid";
   }

}

############################### End CostException.java ####################

############################### CategoryException.java ####################

package lib;

public class CategoryException extends Exception {

   public CategoryException() {
        super("Category value Invalid \n");
   }  

   public String getMesg() {
       return "Category value Invalid";
   }

}

############################### End CategoryException.java ####################

############################### InputMismatchException.java ####################

package lib;

public class InputMismatchException extends Exception {

   public InputMismatchException() {
        super("Input Number Invalid \n");
   }  

   public String getMesg() {
       return "Input Number Invalid";
   }

}

############################### End InputMismatchException.java ####################

############################### Output0 ####################

usr@DESKTOP-VUMS 26N:/mnt/i/PRJ/Code/jv/lib$ java Book Exceptions Demo Enter number of Books : -1 Invalid Number of books : Enter number of Books : Invalid Number of books : Enter number of Books : Enter Pages : -1 Invalid Pages Enter Pages : Invalid Pages Enter Pages : Enter Cost : -1 Invalid Cost Enter Cost : Enter Category of Books : abc Invalid Category Enter Category of Books : Text Enter Pages :

############################### End Output0####################

############################### Output1 ####################

Invalid Pages Enter Pages : Enter Cost : Invalid Cost Enter Cost : Enter Category of Books : abc Invalid Category Enter Category of Books : Text Enter Pages : 20 Enter Cost : 200 Enter Category of Books : Fiction Enter Pages : 30 Enter Cost : 400 Enter Category of Books : Non-Fiction Category : Text Pages : 3 Cost : @ Category : Fiction Pages : 20 Cost : 200 Category : Non-Fiction Pages : 30 Cost : 400 usr@DESKTOP-VUM526N:/mnt/i/PRJ/Code/jw/lib$

############################### End Output1####################