public void addFruits(String fruitName, int quantity) {
        Integer curQuantity = entry.get(fruitName);
        if (curQuantity != null) {
            entry.put(fruitName, curQuantity + quantity);
        }
        else {
            throw new IllegalArgumentException("Not found fruit with name: " + fruitName);
        }
    }
public void addFruits(String fruitName, int quantity)