private double productSum;

private final HashMap<Product, Integer> order = new HashMap<>();

public void addProduct (Product product, int quantity) {

if (order.containsKey(product)) {

int oldQuantity = order.get(product);

int newQuantity = oldQuantity + quantity;

order.put(product, newQuantity);

}else {

order.put(product, quantity);

}

productSum = calculate();

}

private double calculate() {

double sum = 0;

for (Product product : order.keySet()){

int quantity = order.get(product);

sum += product.price * quantity;

}

return sum;

}

public void showProduct(){

System.out.println("Список товаров: ");

for (Product product : order.keySet()){

System.out.println(product.name + " " + String.format("%.2f", product.price));

}

}

public double getProductsum(){return productSum;}

public String rublesFormat(double rubles) {

int lastDigit = (int) (Math.floor(rubles) % 10);

if (((int) (Math.floor(rubles) % 100)) <= 19 && ((int)(Math.floor(rubles) % 100)) >= 11)

return "рублей";

switch (lastDigit) {

case 1:

return "рубль";

case 2:

case 3:

case 4:

return "рубля";

default:

return "рублей";

}

}