Refactoring

Refactoring Example

// Before Refactoring
class Order {
    public double calculateTotal() {
        double total = 0;
        for(Item item : items) {
            // Calculate price
            double price = item.getPrice();
            // Add tax
            price = price * 1.2;
            // Apply discount if quantity > 10
            if(item.getQuantity() > 10) {
                price = price * 0.9;
            }
            total += price * item.getQuantity();
        }
        return total;
    }
}

// After Refactoring
class Order {
    private static final double TAX_RATE = 1.2;
    private static final double BULK_DISCOUNT = 0.9;
    private static final int BULK_THRESHOLD = 10;

    public double calculateTotal() {
        return items.stream()
            .mapToDouble(this::calculateItemTotal)
            .sum();
    }

    private double calculateItemTotal(Item item) {
        return applyDiscount(
            calculatePriceWithTax(item),
            item.getQuantity()
        ) * item.getQuantity();
    }

    private double calculatePriceWithTax(Item item) {
        return item.getPrice() * TAX_RATE;
    }

    private double applyDiscount(double price, int quantity) {
        return quantity > BULK_THRESHOLD 
            ? price * BULK_DISCOUNT 
            : price;
    }
}