How to calculate average value from an ArrayList

Question

I am trying to calculate the average value from a shopping cart (ArrayList). Average value means the sum all the products divided by its quantity?, correct me If I am wrong please maybe that's why my logic is not working well.

I was trying to do a loop for calculating the sum of all the products and then divided by its quantity.

public double getAverageValue(){
    double averageValue = 0;

    for ( int i=0; i < cartLineList.size() ; i++) {
        double sum += cartLineList.get(i).getProduct();
    }

    for (CartLine cart : cartLineList) {
        averageValue = (sum / cart.getQuantity());
    }
    return averageValue;
}

public class CartLine {

private Product product;
private int quantity;

public CartLine(Product product, int quantity) {
    this.product = product;
    this.quantity = quantity;
}

public double getSubtotal() {
    return quantity * product.getPrice();
}

public Product getProduct() {
    return product;
}

public void setProduct(Product product) {
    this.product = product;
}

public int getQuantity() {
    return quantity;
}

public void setQuantity(int quantity) {
    this.quantity = quantity;
}
}

Answer 1

try something like this

public double getAverageValue(){
  double averageValue = 0;
  double sum = 0;

  if(cartLineList.size() > 0){
    for ( int i=0; i < cartLineList.size() ; i++) {
      // assuming the product class has a price
      sum += cartLineList.get(i).getProduct().getPrice();
    }
    averageValue = (sum / (double)cartLineList.size())
  }

  return averageValue;
}