Question

Use exceptions to correct errors and please don't use stacks

2. Write a class called ShoppingBag to keep track of items purchased. The ShoppingBag contains a summary of an order. It will implement the Retail interface (given below) and will need some additional methods to place items in the bag and to output the bags current status. ShoppingBag contains the total cost of items purchased (before tax), the total after tax, the number of items in the bag, and the average cost ofan item. A. Create the following interface and use it when implementing the ShoppingBag class. a. public interface Retail total cost of all items before tax double RetailCost0; double AverageCost0; average cost of an item, before tax double TotalCost0; ll total cost of all items including tax ll number of items in the bag int Totalltems0; B. create a class called shoppingBag that implements the Retail interface. objects of this class represent a single shopping bag. Attributes of such an object include the number of items in the bag, the tax rate and the retail cost of those items. a. Create a constructor that accepts a tax rate as a double argument. b. Create a method called Buy that puts an item into the bag. accepts indicates argument indicating the quantity purchased and a double argument that five the of the item. For example, myBag.Buy(5, 10.50) represents buying items that cost 10.50 each.

Answer 1

/* JAVA Program to implement a shoppingbag application .
Prigram reads lines from a file and computes total number of items, total cost,
average cost, and use exception to count number of line contains invalid input
*/
import java.util.*;
import java.io.*;
//interface defined
interface Retail
{
   public double RetailCost();
   public double AverageCost();
   public double TotalCost();
   public int TotalItems();
}
//class defination
class ShoppingBag implements Retail
{
   private int noOfItems;
   private double taxRate;
   private double retailCost;
   //constructor to accept tax rate
   public ShoppingBag(double trate)
       {
           noOfItems=0;
           retailCost=0.00;
           taxRate=trate;
       }
//this method accepts number of items purchased ,and cost per item add it to the bag
   public void Buy(int n,double cost)
   {
       noOfItems+=n;
       retailCost=retailCost+(n*cost);
   }
//this method return retail cos\t
public double RetailCost()
   {
       return retailCost;
   }
//this method return average cost
public double AverageCost()
   {
   return (retailCost/noOfItems)   ;
   }
//this method return total cost after adding tax
public double TotalCost()
{
   double tax=retailCost*taxRate/100;
   return retailCost+tax;
}
//this method return number of items in bag
public int TotalItems()
   {
       return noOfItems;
   }
//retiurns a string containing output.
public String toString()
   {
   String s;
   s="Items :"+noOfItems+"\nRetail cost :$"+retailCost+"\nAverage item cost : $"+AverageCost();
   s+="\nTotal cost including tax("+taxRate+") : $"+TotalCost();
   return s;
   }

}

/////////////////////////////////////////
// main class
public class ShoppingBagApp
   {
       public static void main(String arg[]) throws FileNotFoundException
           {

           ShoppingBag bag=new ShoppingBag(7.00);
           int n,counterror=0;

           double cost;
           File file=new File("retail.txt");
           Scanner fin=new Scanner(file); // load file
           //read file until end
           while(fin.hasNext() )
               {
               try
                   {
                   if(fin.hasNextInt() || fin.hasNextDouble()) // check for valid input
                       {
                       n=fin.nextInt();
                       cost=fin.nextDouble();
                       bag.Buy(n,cost); //call to Buy()
                       }
                   else
                       {
                           throw new NumberFormatException();
                       }
                   }
           //catch block to count number of invalid input
           catch(NumberFormatException e)
                   {
                   counterror++;
                   fin.nextLine();
                   fin.nextLine();
                   }

               }
           System.out.println(bag);
           System.out.println("\n\nTherer were "+counterror + " lines of input skipped due to input mismatch exception");
       }
   }

------------------------------------------------------------------

//output

null