What are some examples of the Strategy Pattern in Java?

What are some examples of the Strategy Pattern in Java?

The Strategy Pattern is a behavioral design pattern that enables selecting an algorithm's behavior at runtime. For example, in a payment processing system, you could have different payment strategies like CreditCardPayment, PayPalPayment, and BitcoinPayment.

Can you show me a code example of the Strategy Pattern?

Sure! Here's a simple example:

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

// Concrete Strategies
class CreditCardPayment implements PaymentStrategy {
    public void pay(int amount) {
        System.out.println("Paid " + amount + " using Credit Card.");
    }
}

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

// Context
class ShoppingCart {
    private PaymentStrategy paymentStrategy;

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

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

In this example, the ShoppingCart can use different payment strategies.

How do I implement this in my project?

To implement the Strategy Pattern in your project, define the strategy interface and concrete strategy classes as shown in the example. Then, in your context class (like ShoppingCart), you can set the desired strategy at runtime based on user input or other conditions.