Real World Example

Example

public class Main {
    public static void main(String[] args) {
        Cart cart = new Cart("Neha");
        cart.add(new CartItem("Running Shoes", 2499, 1));
        cart.add(new CartItem("Sports Socks", 199, 3));
        cart.add(new CartItem("Water Bottle", 349, 2));
        cart.printSummary();
    }
}

class CartItem {
    String name;
    double price;
    int qty;

    CartItem(String name, double price, int qty) {
        this.name = name;
        this.price = price;
        this.qty = qty;
    }

    double lineTotal() {
        return price * qty;
    }
}

class Cart {
    String owner;
    CartItem[] items = new CartItem[10];
    int size = 0;

    Cart(String owner) {
        this.owner = owner;
    }

    void add(CartItem item) {
        items[size++] = item;
    }

    double total() {
        double sum = 0;
        for (int i = 0; i < size; i++) sum += items[i].lineTotal();
        return sum;
    }

    void printSummary() {
        System.out.println(owner + "'s cart");
        for (int i = 0; i < size; i++) {
            CartItem it = items[i];
            System.out.printf("  %-14s %d x %7.2f = %8.2f%n", it.name, it.qty, it.price, it.lineTotal());
        }
        double total = total();
        double delivery = total >= 999 ? 0 : 49;
        System.out.printf("  Items total: %.2f, Delivery: %.2f, Pay: %.2f%n", total, delivery, total + delivery);
    }
}

Output

Neha's cart
  Running Shoes  1 x 2499.00 =  2499.00
  Sports Socks   3 x  199.00 =   597.00
  Water Bottle   2 x  349.00 =   698.00
  Items total: 3794.00, Delivery: 0.00, Pay: 3794.00