public class ShoppingCartUsage {
    public static void main(String[] args) {
        // Επιλογή 1: Πληρωμή με PayPal
        ShoppingCart cart1 = new ShoppingCart(150.75);
        cart1.setPaymentStrategy(new PayPalStrategy("user@example.com"));
        cart1.checkout();

        // Επιλογή 2: Ο χρήστης αλλάζει γνώμη και βάζει κάρτα
        ShoppingCart cart2 = new ShoppingCart(23.5);
        cart2.setPaymentStrategy(new CreditCardStrategy("John Doe", "1234-5678-9012"));
        cart2.checkout();
        
        ShoppingCart cart3 = new ShoppingCart(18.20);
        cart3.setPaymentStrategy(new CreditCardStrategy("Marry Roberts", "9012-5678-1234"));
        cart1.setPaymentStrategy(new PayPalStrategy("marry.roberts@hello.com"));
        cart3.checkout();
    }
}