Shopping cart

import java.util.List;

// CartItem Interface
public interface CartItem {
    String getId();
    String getName();
    double getPrice();
    int getQuantity();
    void setQuantity(int quantity);
}

// ShoppingCart Interface
public interface ShoppingCart {
    void addItem(CartItem item);
    void removeItem(String itemId);
    CartItem getItem(String itemId);
    List<CartItem> getItems();
    double getTotalPrice();
    void clearCart();
    Customer getCustomer();
    void setCustomer(Customer customer);
}

// PaymentProcessor Interface
public interface PaymentProcessor {
    boolean processPayment(double amount, String paymentMethod);
}

// CartManager Interface
public interface CartManager {
    void checkout(ShoppingCart cart, PaymentProcessor paymentProcessor, String paymentMethod);
    void applyDiscount(ShoppingCart cart, double discount);
    void registerCustomer(Customer customer);
}

// Customer Interface
public interface Customer {
    String getId();
    String getName();
    String getEmail();
    void setEmail(String email);
}
Implementations
SimpleCartItem Class
java
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public class SimpleCartItem implements CartItem {
    private String id;
    private String name;
    private double price;
    private int quantity;

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

    @Override
    public String getId() {
        return id;
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public double getPrice() {
        return price;
    }

    @Override
    public int getQuantity() {
        return quantity;
    }

    @Override
    public void setQuantity(int quantity) {
        this.quantity = quantity;
    }
}
SimpleShoppingCart Class
java
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import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

public class SimpleShoppingCart implements ShoppingCart {
    private Map<String, CartItem> items = new HashMap<>();
    private Customer customer;

    @Override
    public void addItem(CartItem item) {
        items.put(item.getId(), item);
    }

    @Override
    public void removeItem(String itemId) {
        items.remove(itemId);
    }

    @Override
    public CartItem getItem(String itemId) {
        return items.get(itemId);
    }

    @Override
    public List<CartItem> getItems() {
        return items.values().stream().collect(Collectors.toList());
    }

    @Override
    public double getTotalPrice() {
        return items.values().stream()
                .mapToDouble(item -> item.getPrice() * item.getQuantity())
                .sum();
    }

    @Override
    public void clearCart() {
        items.clear();
    }

    @Override
    public Customer getCustomer() {
        return customer;
    }

    @Override
    public void setCustomer(Customer customer) {
        this.customer = customer;
    }
}
CreditCardPaymentProcessor Class
java
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public class CreditCardPaymentProcessor implements PaymentProcessor {
    @Override
    public boolean processPayment(double amount, String paymentMethod) {
        // Implement payment processing logic here
        System.out.println("Processing payment of " + amount + " using " + paymentMethod);
        return true; // Return true if payment is successful
    }
}
SimpleCartManager Class
java
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public class SimpleCartManager implements CartManager {
    @Override
    public void checkout(ShoppingCart cart, PaymentProcessor paymentProcessor, String paymentMethod) {
        double total = cart.getTotalPrice();
        if (paymentProcessor.processPayment(total, paymentMethod)) {
            cart.clearCart();
            System.out.println("Checkout successful for customer: " + cart.getCustomer().getName());
        } else {
            System.out.println("Checkout failed for customer: " + cart.getCustomer().getName());
        }
    }

    @Override
    public void applyDiscount(ShoppingCart cart, double discount) {
        // Apply discount logic
        System.out.println("Discount of " + discount + " applied.");
    }

    @Override
    public void registerCustomer(Customer customer) {
        // Registration logic (if needed)
        System.out.println("Customer registered: " + customer.getName());
    }
}
SimpleCustomer Class
java
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public class SimpleCustomer implements Customer {
    private String id;
    private String name;
    private String email;

    public SimpleCustomer(String id, String name, String email) {
        this.id = id;
        this.name = name;
        this.email = email;
    }

    @Override
    public String getId() {
        return id;
    }

    @Override
    public String getName() {
        return name;
    }

    @Override
    public String getEmail() {
        return email;
    }

    @Override
    public void setEmail(String email) {
        this.email = email;
    }
}