Could you tell about your experience implementing the strategy pattern in projects?

I used the strategy pattern to implement flexible discount calculation logic in an online store. Instead of hard-coded conditions, each discount strategy was encapsulated in a separate class implementing a common interface. This allowed easy addition of new discount types without modifying existing code.

Example in Java:

interface DiscountStrategy {
    double applyDiscount(double price);
}

class NoDiscount implements DiscountStrategy {
    public double applyDiscount(double price) {
        return price;
    }
}

class PercentageDiscount implements DiscountStrategy {
    private double percent;
    public PercentageDiscount(double percent) {
        this.percent = percent;
    }
    public double applyDiscount(double price) {
        return price * (1 - percent / 100);
    }
}

class ShoppingCart {
    private DiscountStrategy discountStrategy;

    public ShoppingCart(DiscountStrategy discountStrategy) {
        this.discountStrategy = discountStrategy;
    }

    public double calculatePrice(double price) {
        return discountStrategy.applyDiscount(price);
    }
}

This approach improved the extensibility and testability of the code.