如何从ArrayList计算平均值

Question

我试图从购物车（ArrayList）中计算平均值。平均值是指所有产品的总和除以它的数量？，如果我错了请纠正我，也许这就是为什么我的逻辑不太好用。

我试图做一个循环来计算所有乘积的总和，然后除以它的数量。

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

试试这样的东西

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;
}