[NP] Shopping Cart

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;

abstract class Product implements Comparable<Product> {
    private String id;
    private String name;
    private int price;

    public Product(String id, String name, int price) {
        this.id = id;
        this.name = name;
        this.price = price;
    }

    public String getId() {
        return id;
    }

    public abstract float getTotalPrice();

    public String getName() {
        return name;
    }

    public int getPrice() {
        return price;
    }
}

class ProductPerKilogram extends Product{
    private float quantity;

    public ProductPerKilogram(String id, String name, int price, float quantity) {
        super(id, name, price);
        this.quantity= quantity;
    }

    public float getTotalPrice(){
        return super.getPrice()*quantity/1000.0f;
    }

    @Override
    public int compareTo(Product o) {
        return Float.compare(this.getTotalPrice(),o.getTotalPrice());
    }

    @Override
    public String toString() {
        return String.format("%s - %.2f",super.getId(),getTotalPrice());
    }
}

class WholeProduct extends Product{

    private float quantity;

    public WholeProduct(String id, String name, int price, int quantity) {
        super(id, name, price);
        this.quantity= quantity;
    }

    public float getTotalPrice(){
        return super.getPrice()*quantity;
    }

    @Override
    public int compareTo(Product o) {
        return Float.compare(this.getTotalPrice(),o.getTotalPrice());
    }
    @Override
    public String toString() {
        return String.format("%s - %.2f",super.getId(),getTotalPrice());
    }

}


class InvalidOperationException extends Exception{
    public InvalidOperationException(String message) {
        super(message);
    }
}

public class ShoppingTest {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        ShoppingCart cart = new ShoppingCart();

        int items = Integer.parseInt(sc.nextLine());
        for (int i = 0; i < items; i++) {
            try {
                cart.addItem(sc.nextLine());
            } catch (InvalidOperationException e) {
                System.out.println(e.getMessage());
            }
        }

        List<Integer> discountItems = new ArrayList<>();
        int discountItemsCount = Integer.parseInt(sc.nextLine());
        for (int i = 0; i < discountItemsCount; i++) {
            discountItems.add(Integer.parseInt(sc.nextLine()));
        }

        int testCase = Integer.parseInt(sc.nextLine());
        if (testCase == 1) {
            cart.printShoppingCart(System.out);
        } else if (testCase == 2) {
            try {
                cart.blackFridayOffer(discountItems, System.out);
            } catch (InvalidOperationException e) {
                System.out.println(e.getMessage());
            }
        } else {
            System.out.println("Invalid test case");
        }
    }
}

class ShoppingCart {
    List<Product> products;

    public ShoppingCart() {
        this.products = new ArrayList<>();
    }

    public void addItem(String s) throws InvalidOperationException {
        String[] parts= s.split(";");
        String id = parts[1];
        String name = parts[2];
        int price = Integer.parseInt(parts[3]);
        float quantity = Float.parseFloat(parts[4]);
        if(quantity==0){
            throw new InvalidOperationException(String.format("The quantity of the product with id %s can not be 0.",id));
        }
        if(parts[0].equals("WS")){
            products.add(new WholeProduct(id,name,price,(int)quantity));
        }
        else{
            products.add(new ProductPerKilogram(id,name,price,quantity));
        }
    }

    public void printShoppingCart(PrintStream out) {

        PrintWriter printWriter= new PrintWriter(out);

        products.stream().sorted(Comparator.reverseOrder()).forEach(i->printWriter.println(i));

        printWriter.flush();
    }

    public void blackFridayOffer(List<Integer> discountItems, PrintStream out) throws InvalidOperationException {
        PrintWriter printWriter= new PrintWriter(out);
        if(discountItems.size()==0)
            throw new InvalidOperationException("There are no products with discount.");

        products.stream()
                .filter(i->discountItems.contains(Integer.parseInt(i.getId())))
                .map(i -> i.getId() + " - " + String.format("%.2f", i.getTotalPrice() * 0.1f))
                .forEach(i -> printWriter.println(i));
        printWriter.flush();
    }
}