Question

​I have to create two classes one class that accepts an object, stores the object in an array. I have another that has a constructor that creates an object.

Here is my first class named "ShoppingList":

import java.util.*;
public class ShoppingList
{
   private ShoppingItem [] list;
   private int amtItems = 0;
  
   public ShoppingList()
   {
      list=new ShoppingItem[8];
   }
  
   public void add(ShoppingItem item)
   {
      if(amtItems<8)
      {
         list[amtItems] = ShoppingItem(item);
         amtItems++;
      }
      else
         System.out.println("Your item's have exceeded the amount of items that can fit in the bag.");     
   }
  
   public void add(String item, int amt, double cost)
   {
      if(amtItems<8)
      {
         list[amtItems] = new ShoppingItem(item, amt, cost);
         amtItems++;
      }
      else
         System.out.println("Your item's have exceeded the amount of items that can fit in the bag.");
   }
  
   public double getTotalCost()
   {
      double totalCost = 0;
      for(int i = 0; i          totalCost+=list[i].getCost();
      return totalCost;
   }
  
   public String toString()
   {
      for(int i = 0;i       {
         if(i==0)
            System.out.println("This shopping list has " + amtItems + " shopping items: " + list[i].toString());
         else
            System.out.println(", " + list[i].toString);
      }
      return"";
   }
}

​Here is my second class called "ShoppingItem":

public class ShoppingItem
{
   private String itemName;
   private int amount;
   private double pricePU;
  
   public ShoppingItem(String x, int y, double z)
   {
      this.itemName = x;
      this.amount=y;
      this.pricePU=z;
   }
  
   public double getCost()
   {
      return this.amount*this.pricePU;
   }
  
   public void setQuantity(int x)
   {
      this.amount=x;
   }
  
   public String toString()
   {
      return (this.amount + " " + this.itemName);
   }
}

The teacher created a test program to test our algorithms, the constructors in ShoppingItem seem to work. I bolded the area's in ShoppingList that seem to be disagreeing. The second add function was me playing around with different ideas. Her exact line is "g.add( new ShoppingItem("Tissues", 4, 2.30));​". So since this part works "ShoppingItem go = new ShoppingItem("Milk", 2, 3.75);​" I think my costructor is fine in ShoppingItem. I think my problem is I don't know how to accept an object in my shopping list constructor and save it to my array of objects.

Oh, my .toString function in ShoppingList also has a compiler error if you get a chance to look at it, but I figure I can probably figure that one out.

​Here is the teacher's client:

/* Use this client program to test your class implementations
*
*/
import java.util.*;
public class ShoppingListClient {
   public static final int N = 1;
   public static final double DISCOUNT = 0.1;
  
   public static void main (String [] args) {
      System.out.println("Creating ShoppingList");
  ShoppingList g = new ShoppingList();
  System.out.println("Creating new ShoppingItem");
  ShoppingItem go = new ShoppingItem("Milk", 2, 3.75);
  System.out.println("Changing the quantity to 3");
  go.setQuantity( 3 );
  System.out.println("The total cost should be 11.25. It is actually: " + go.getCost() );
  System.out.println("Adding ShoppingItems to ShoppingList");
  g.add( go );
  g.add( new ShoppingItem("Tissues", 4, 2.30));
      g.add (new ShoppingItem ("Toothpaste", 1, 4));
      g.add (new ShoppingItem ("Eggs", 12, 0.50));
      g.add (new ShoppingItem ("Apples", 5, 2.99));
      g.add (new ShoppingItem ("Bananas", 4, 0.99));
   
      System.out.println (g.toString());
  System.out.println("The total cost of shopping list should be 49.36. It is actually: " + g.getTotalCost() );
     
      Scanner input = new Scanner (System.in);
      System.out.print ("Enter the customer name: ");
      String name = input.next();
      for (int i=0; i<N; i++) {
         System.out.print ("Enter the shopping item: ");
         String shoppingItemName = input.next();
         System.out.print ("Enter the quantity: ");
         int quan = input.nextInt();
         System.out.print ("Enter the price per unit: ");
         double ppu = input.nextDouble();
         g.add (new ShoppingItem (shoppingItemName, quan, ppu));
         System.out.println (g.toString());

      }
   }
}

Answer 1

import java.util.*;

public class ShoppingList

{

private ShoppingItem [] list;

private int amtItems = 0;

  

public ShoppingList()

{

list=new ShoppingItem[8];

}

  

public void add(ShoppingItem item)

{

if(amtItems<8)

{

// here you are already passing object of class ShoppingItem and you have an array of

// ShoppingItem type, so you just need to assign ShoppingItem class object item into

// i'th index of array

list[amtItems] = item;

amtItems++;

}

else

System.out.println("Your item's have exceeded the amount of items that can fit in the bag.");

}

  

public void add(String item, int amt, double cost)

{

if(amtItems<8)

{

list[amtItems] = new ShoppingItem(item, amt, cost);

amtItems++;

}

else

System.out.println("Your item's have exceeded the amount of items that can fit in the bag.");

}

  

public double getTotalCost()

{

double totalCost = 0;

for(int i = 0; i<amtItems; i++)

totalCost+=list[i].getCost();

return totalCost;

}

  

public String toString()

{

for(int i = 0;i<amtItems;i++) {

if(i==0)

System.out.println("This shopping list has " + amtItems + " shopping items: " + list[i].toString());

else

System.out.println(", " + list[i].toString()); // in .toString method parenthesis were missing

}

return"";

}

}