Can you give an example of using a behavioral pattern in software design?

Behavioral design patterns describe ways objects interact and responsibilities are distributed.

Example: the "Strategy" pattern.

It allows defining a family of algorithms, encapsulating each one, and making them interchangeable. This helps change the behavior of an object at runtime without modifying its code.

Example in Java:

// Strategy interface
interface PaymentStrategy {
    void pay(int amount);
}

// Concrete strategies
class CreditCardPayment implements PaymentStrategy {
    public void pay(int amount) {
        System.out.println("Credit card payment: " + amount);
    }
}

class PayPalPayment implements PaymentStrategy {
    public void pay(int amount) {
        System.out.println("PayPal payment: " + amount);
    }
}

// Context
class ShoppingCart {
    private PaymentStrategy paymentStrategy;

    public void setPaymentStrategy(PaymentStrategy strategy) {
        this.paymentStrategy = strategy;
    }

    public void checkout(int amount) {
        paymentStrategy.pay(amount);
    }
}

// Usage
ShoppingCart cart = new ShoppingCart();
cart.setPaymentStrategy(new CreditCardPayment());
cart.checkout(1000);

cart.setPaymentStrategy(new PayPalPayment());
cart.checkout(2000);