Strategy design pattern

What is Strategy design pattern?

The strategy design pattern is a behavioral design pattern that defines a family of algorithms, encapsulates each algorithm, and makes the algorithms interchangeable within that family. It allows the client to choose the appropriate algorithm at runtime without changing the client's code.

By using the strategy pattern, the client can easily switch between different algorithms or strategies based on the context or requirements. This pattern promotes code reusability, improves maintainability, and reduces code duplication.

Strategy design pattern advantages:

1. Encourages modular code: The Strategy pattern helps in breaking down complex algorithms or behaviors into smaller, more manageable pieces. This makes code easier to maintain, understand, and reuse.

2. Promotes code reusability: By encapsulating algorithms or behaviors into separate objects, they can be easily swapped and reused in different contexts or by different clients.

3. Enhances flexibility: By using the Strategy pattern, the behavior of an object can be easily modified or extended without altering its structure. This allows for more flexible and adaptable code.

4. Improves testability: With Strategy pattern, it is easier to test individual strategies independently, leading to more reliable and efficient testing.

5. Promotes decoupling: The Strategy pattern separates the implementation of an algorithm from the client that uses it. This reduces dependencies between classes, resulting in more flexible and maintainable code.

6. Makes code more extensible: Adding new strategies to the system is straightforward and does not require changing existing code. This allows for easy expansion of functionality without disrupting the existing codebase.

Steategy design pattern Java example:

Payment method strategy design pattern is a behavioral design pattern that allows the client to choose from a variety of payment methods without changing the client code. It encapsulates the payment methods in separate classes, making it easy to add new payment methods without modifying the existing code.

1. Define the strategy interface:

?public interface PaymentStrategy {
    public void pay(int amount);
}
        

1. Implement multiple strategy classes:

?public class CreditCardPaymentStrategy implements PaymentStrategy {
    @Override
    public void pay(int amount) {
        System.out.println("Paying with credit card: " + amount);
    }
}

public class PayPalPaymentStrategy implements PaymentStrategy {
    @Override
    public void pay(int amount) {
        System.out.println("Paying with PayPal: " + amount);
    }
}
        

1. Create a context class to use the strategy:

?public class PaymentContext {
    private PaymentStrategy paymentStrategy;
    
    public PaymentContext(PaymentStrategy paymentStrategy) {
        this.paymentStrategy = paymentStrategy;
    }
    
    public void performPayment(int amount) {
        paymentStrategy.pay(amount);
    }
}
        

1. Use the context class with different strategies at runtime:

public class Main {
    public static void main(String[] args) {
        PaymentContext context = new PaymentContext(new CreditCardPaymentStrategy());
        context.performPayment(100);
        
        context = new PaymentContext(new PayPalPaymentStrategy());
        context.performPayment(50);
    }
}        

Conclusion:

The Strategy design pattern is a powerful tool for managing algorithmic complexities in software systems and promoting code reusability and maintainability.