In this challenge, you will write a method called int countDiscountedItems() in the ShoppingCart class. This method will use a loop to traverse the ArrayList of Items called order.

In the loop, you will test if each Item is a DiscountedItem by using the instanceof keyword ((object instanceof Class) returns true or false) similar to its use in the add(Item) method.

If it is a DiscountedItem, then you will count it.

At the end of the loop, the method will return the count.

Make sure you print out the number of discounted items in the main method or in printOrder(), so that you can test your method. Add more items to the order to test it.

Copy in your code for DiscountedItem below and then write a method called countDiscountedItems which traverses the polymorphic ArrayLists of Items. Use instanceOf to test items to see if they are a DiscountedItem.

import java. util.*;

/**
The ShoppingCart class has an ArrayList of Items.
You will write a new class DiscountedItem that extends Item.
This code is adapted https://practiceit. cs. washington. edu/problem/view/bjp4/chapter9/e10- DiscountBill
*/

public class Tester
{
public static void main(String[] args) {
ShoppingCart cart = new ShoppingCart();
cart. add(new Item("bread", 3.25));
cart. add(new Item("milk", 2.50));
//cart. add(new DiscountedItem("ice cream", 4.50, 1.50));
//cart. add(new DiscountedItem("apples", 1.35, 0.25));

cart. printOrder();
}
}

class DiscountedItem extends Item
{
// Copy your code from the last lesson's challenge here!
}

// Add a method called countDiscountedItems()
class ShoppingCart
{
private ArrayList order;
private double total;
private double internalDiscount;

public ShoppingCart()
{
order = new ArrayList();
total = 0.0;
internalDiscount = 0.0;
}

public void add(Item i) {
order. add(i);
total += i. getPrice();
if (i instanceof DiscountedItem)
internalDiscount += ((DiscountedItem) i).getDiscount();
}

/** printOrder() will call toString() to print */
public void printOrder() {
System. out. println(this);
}

public String toString() {
return discountToString();
}

public String discountToString() {
return orderToString() + "\nSub-total: " + valueToString(total) + "\nDiscount: " + valueToString(internalDiscount) + "\nTotal: " + valueToString(total - internalDiscount);
}

private String valueToString(double value) {
value = Math. rint(value * 100) / 100.0;
String result = "" + Math. abs(value);
if(result. indexOf(".") == result. length() - 2) {
result += "0";
}
result = "$" + result;
return result;
}

public String orderToString() {
String build = "\nOrder Items:\n";
for(int i = 0; i < order. size(); i++) {
build += " " + order. get(i);
if(i != order. size() - 1) {
build += "\n";
}
}
return build;
}
}

class Item {
private String name;
private double price;

public Item()
{
this. name = "";
this. price = 0.0;
}

public Item(String name, double price) {
this. name = name;
this. price = price;
}

public double getPrice() {
return price;
}

public String valueToString(double value) {
String result = "" + Math. abs(value);
if(result. indexOf(".") == result. length() - 2) {
result += "0";
}
result = "$" + result;
return result;
}

public String toString() {
return name + " " + valueToString(price);
}
}