Refactoring and Code Smells

Welcome to the world of refactoring! In this lesson, we're learning about Code Smells, which are patterns in code that hint at potential problems. Our mission is to help you spot these smells and understand how to improve them or, in programming terms, how to refactor them. We'll delve into the concept of code smells, examine different types, and apply real-world code examples to solidify your understanding. Let's get started!

Code smells are signs that something could be amiss in our code. You could compare them to an unpleasant smell in a room. But instead of indicating rotten food or a dirty sock, they signal that our code may not be as readable, efficient, or manageable as it could be.

Consider this bit of code:

public class PriceCalculator {
    public static int calculate(int quantity, int price) {
        return quantity * price;
    }

    public static void main(String[] args) {
        int total = calculate(5, 3);
        System.out.println(total);
    }
}

The function name calculate is too vague. What exactly does it calculate? For whom? This ambiguity is a sign of a bad naming code smell.

If you notice the same piece of code in more than one place, you may be looking at an example of the Duplicate Code smell. Duplicate code leaves room for errors and bugs. If you need to make a change, you might overlook one instance of duplication.

Here's an example:

int totalApplesPrice = quantityApples * priceApple - 5;
int totalBananasPrice = quantityBananas * priceBanana - 5;

This code performs the same operation on different data. Instead of duplicating the operation, we can create a method to handle it:

public class PriceCalculator {
    public static int calculatePrice(int quantity, int price) {
        int discount = 5;
        return quantity * price - discount;
    }

    public static void main(String[] args) {
        int totalApplesPrice = calculatePrice(quantityApples, priceApple);
        int totalBananasPrice = calculatePrice(quantityBananas, priceBanana);
        System.out.println(totalApplesPrice);
        System.out.println(totalBananasPrice);
    }
}

With this solution, if we need to change the discount or the formula, we can do so in one place: the calculatePrice method.