ShoppingCartFactory

package cashregister;

public class ShoppingCartFactory extends Object {

    private static long SHOPPING_CART_ID = 1;

    public ShoppingCartFactory() {}

    public static IShoppingCart createShoppingCart() {
        return new ShoppingCart(SHOPPING_CART_ID++);
        }

    public static IShoppingCart createShoppingCart(long id) {
        if(SHOPPING_CART_ID < id) {
            return new ShoppingCart(id++);
        }
        return new ShoppingCart(SHOPPING_CART_ID++);
    }

    }