Lesson 5
Stepping into Refactoring Code in Java
Stepping into Refactoring Code

Welcome to our captivating session on refactoring, a powerful tool for tidying up code, much like you would organize a messy toy box or find a faster route to school.

As each line of code is as essential as a brick in a building, clumsy code may result in an unstable structure. Today, we'll focus on enhancing the readability, maintainability, and performance of our code through refactoring.

Recapping Crucial Concepts

Let's briefly revisit a few key concepts:

  • Code Smells: Indicators that our code needs refactoring, akin to clutter calling for cleanup.
  • Refactoring Techniques: We've familiarized ourselves with Extract Method, Rename Method, and Substitute Algorithm techniques in earlier lessons.
  • OOP in Refactoring: We've learned how to leverage Object-Oriented Programming principles to enhance our code's structure.
  • Code Decoupling and Modularization: Methods to make code easier to manage by minimizing dependencies.

We'll use these concepts as guiding stars as we traverse the cosmos of refactoring.

Practice Problem 1: Taming a Complex Function

We'll start by rewriting a complex game score computation function. Let's look at it:

Java
1public class Game {
2    public static int computeScore(Player player, List<Integer> monsters) {
3        int score = 0;
4        for (int monster : monsters) {
5            if (player.getPower() > monster) {
6                score += player.getPower() - monster;
7            } else {
8                score -= player.getPower() - monster;
9            }
10        }
11        return score;
12    }
13}

This code uses some algorithm to adjust the score based on the player's and monster's power. The parts player.getPower() > monster and player.getPower() - monster recur in this function, indicating room for refactoring. We'll apply the Extract Method and Rename Method to untangle this:

  • We'll extract the scoring logic into a separate function, scoreChange.
  • We'll rename the original function to computeGameScore.

With these adjustments, our improved code might look something like this:

Java
1// New function to calculate score changes.
2public class Game {
3    private static int scoreChange(int power, int monster) {
4        if (power > monster) {
5            return power - monster;
6        } else {
7            return monster - power;
8        }
9    }
10
11    // Refactored function to calculate the game score.
12    public static int computeGameScore(Player player, List<Integer> monsters) {
13        int score = 0;
14        for (int monster : monsters) {
15            score += scoreChange(player.getPower(), monster);
16        }
17        return score;
18    }
19}

This refactoring has simplified the function and made it easier to modify in the future.

Practice Problem 2: Refactoring with OOP and Code Decoupling

Let's consider another example where the game has multiple types of monsters. Each monster type behaves differently when encountered by a player.

Java
1public class Game {
2    public static void monsterReaction(String monsterType, Player player) {
3        if (monsterType.equals("ghost")) {
4            if (player.getPower() > 5) {
5                System.out.println("The ghost flees in terror!");
6            } else {
7                System.out.println("The ghost grumbles and attacks!");
8            }
9        } else if (monsterType.equals("goblin")) {
10            if (player.getPower() > 3) {
11                System.out.println("The goblin groans and retreats!");
12            } else {
13                System.out.println("The goblin hacks with its sword!");
14            }
15        }
16        // more monster types...
17    }
18}

This scenario could also benefit from refactoring using OOP and Code Decoupling:

  • First, we'll introduce a class Monster with a method reaction that could be overridden by each type of monster.
  • Then, we'll create child classes Ghost and Goblin that inherit from Monster and implement their own reaction methods.

Under the revised structure, our game code would look like this:

Java
1public abstract class Monster {
2    public abstract void reaction(Player player);
3}
4
5public class Ghost extends Monster {
6    @Override
7    public void reaction(Player player) {
8        if (player.getPower() > 5) {
9            System.out.println("The ghost flees in terror!");
10        } else {
11            System.out.println("The ghost grumbles and attacks!");
12        }
13    }
14}
15
16public class Goblin extends Monster {
17    @Override
18    public void reaction(Player player) {
19        if (player.getPower() > 3) {
20            System.out.println("The goblin groans and retreats!");
21        } else {
22            System.out.println("The goblin hacks with its sword!");
23        }
24    }
25}
26
27// Game class where List of Monsters is managed
28public class Game {
29    public static void main(String[] args) {
30        Player player = new Player(4); // This is just an example instantiation.
31        List<Monster> monsters = Arrays.asList(new Ghost(), new Goblin(), new Ghost(), new Goblin());
32        for (Monster monster : monsters) {
33            monster.reaction(player);
34        }
35    }
36}

Now, our code dealing with multiple monsters is easier to manage and can be extended to accommodate more types of monsters.

Wrapping Up and Looking Ahead

Phew! We've done an excellent job working through two practical problems, enhancing our refactoring skills, and learning how to identify code smells and apply refactoring techniques.

The more you practice, the better you'll become at spotting code that could benefit from refactoring. Brace yourself for more practice tasks, and remember, always keep your code lean and efficient!

Enjoy this lesson? Now it's time to practice with Cosmo!
Practice is how you turn knowledge into actual skills.