Calculation of nettotal using Object class in android

Question

I have a product object which is I'm using to add Product which are adding to the cart.

Product.java object (I have getters and setters),

public class Product {

    public double price;
    public String description;
    public int quantity;
    public String instructions;
    public double subTotal;

    public Product(String description, int quantity, String instructions,
            double subTotal, double price) {

        this.price = price;
        this.description = description;
        this.quantity = quantity;
        this.instructions = instructions;
        this.subTotal = subTotal;
    }
}

This object is belong to each item is been added to the cart. I want to find the net total of each item is being added to the cart. It is like if I have added 3 items to the cart then total of 3 subTotal.

In my activity I tried to access the subtotal by using,

total = Product.subTotal;

then I changed the subtotal to static then all the item prices change to last item added to the cart.

My problem is how can I get the total of each item added to the cart from my activity. So I can find the nettotal. Any advises will be appreciated.

Answer 1

I think you need some more understanding of object oriented programming. static means, that the field (subtotal in your case) does not belong to the Product instance. But since subTotal is a attribute for each instance of Product it may not be static so that its related to Product. Read more on static.

To calculate the total, you have to iterate about your Product instance and sum all subTotals, e.g. like this:

// empty List
List<Product> myProducts = new ArrayList<Product>();
myProducts.add(new Product("description",1, "instructions", 5, 7));
[...]
double total = 0;
for(Product product : myProducts) {
   total += product.subTotal * product.quantity;
}
System.out.println("Total: " + total);