A Developer’s Guide to Refactoring for Better Low-Level Design
Low Level Design
Best Practices

A Developer’s Guide to Refactoring for Better Low-Level Design

S

Shivam Chauhan

14 days ago

Ever stared at your code and thought, "This is a disaster?" You’re not alone. We've all been there. That spaghetti code, those classes that do way too much, and that nagging feeling that everything could be… better.

Refactoring is like giving your code a spa day. It’s about cleaning up the structure, improving readability, and making it easier to maintain without changing what the code actually does.

Why Refactor for Low-Level Design?

Think of your codebase as a house. If the foundation (low-level design) is shaky, the whole structure is at risk. Refactoring helps you:

  • Reduce Complexity: Smaller, focused classes are easier to understand.
  • Improve Readability: Clear code is easier to debug and modify.
  • Increase Maintainability: Well-structured code is simpler to update and extend.
  • Enhance Testability: Focused components are easier to test in isolation.

I remember working on a project where every new feature felt like wrestling an octopus. The code was so intertwined that even small changes created unexpected bugs. Once we started refactoring, it was like night and day. New features became easier to implement, and the overall quality of the code skyrocketed.

Spotting Code Smells: Your Refactoring Radar

Code smells are hints that your code might need some love. Here are a few common ones:

  • Long Methods: Methods that stretch on for pages are hard to understand and maintain.
  • Large Classes: Classes trying to do everything violate the Single Responsibility Principle.
  • Duplicated Code: Copy-pasting code leads to maintenance nightmares.
  • Long Parameter Lists: Too many parameters suggest a class is doing too much.
  • Shotgun Surgery: Changes to one part of the code require changes in many other places.

Refactoring Techniques: Your Toolkit

Here are some go-to refactoring techniques to improve your low-level design:

1. Extract Method

Turn a block of code into its own method. This reduces method length and improves readability.

java
public void processOrder(Order order) {
    // ... lots of code here ...

    // Extract this block into a separate method
    double discount = calculateDiscount(order);
    order.applyDiscount(discount);

    // ... more code ...
}

private double calculateDiscount(Order order) {
    // Discount calculation logic
    return discount;
}

2. Extract Class

Move responsibilities from a large class into a new, focused class. This promotes the Single Responsibility Principle.

java
public class UserProfile {
    private String name;
    private String email;
    private String address;
    // ... other profile details

    // Move address related logic to a new Address class
    public String getFormattedAddress() {
        // ... address formatting logic
    }
}

public class Address {
    private String street;
    private String city;
    private String zipCode;

    public String getFormattedAddress() {
        // ... address formatting logic
    }
}

3. Replace Conditional with Polymorphism

Replace complex if-else or switch statements with polymorphism. This makes the code more flexible and easier to extend.

java
public interface PaymentMethod {
    void processPayment(double amount);
}

public class CreditCardPayment implements PaymentMethod {
    @Override
    public void processPayment(double amount) {
        // ... credit card payment logic
    }
}

public class PayPalPayment implements PaymentMethod {
    @Override
    public void processPayment(double amount) {
        // ... PayPal payment logic
    }
}

// Client code
PaymentMethod paymentMethod = getPaymentMethod();
paymentMethod.processPayment(amount);

4. Introduce Design Patterns

Apply design patterns to solve common design problems. Patterns like Factory, Strategy, and Observer can significantly improve the structure and flexibility of your code.

For example, if you're dealing with different types of notifications, the Factory Design Pattern can help you manage the creation of these notification objects. Check out this blog about Factory Design Pattern for more details.

5. Decompose Conditional

When you have a complex conditional (if-then-else) statement, break it down into smaller, more manageable parts by extracting methods for each condition and action.

java
    public double calculatePrice(Order order) {
        if (isSpecialCustomer(order)) {
            return specialPrice(order);
        } else {
            return regularPrice(order);
        }
    }

    private boolean isSpecialCustomer(Order order) {
        return order.getCustomerType().equals("Special");
    }

    private double specialPrice(Order order) {
        return order.getBasePrice() * 0.9;
    }

    private double regularPrice(Order order) {
        return order.getBasePrice();
    }

6. Replace Type Code with Subclasses

When a class has a type code that affects its behavior, create subclasses for each type to encapsulate the behavior.

java
    public abstract class Employee {
        private int type;

        public abstract int payAmount();
    }

    public class Engineer extends Employee {
        @Override
        public int payAmount() {
            return 10000;
        }
    }

    public class Salesman extends Employee {
        @Override
        public int payAmount() {
            return 5000;
        }
    }

7. Introduce Parameter Object

When a method has too many parameters, encapsulate them into an object to reduce the method signature and improve readability.

java
    public class DeliveryDetails {
        private String receiverName;
        private String address;
        private String city;
        private String zipCode;

        // Constructor, getters, and setters
    }

    public void deliverPackage(DeliveryDetails deliveryDetails) {
        // Use deliveryDetails to deliver the package
    }

8. Preserve Whole Object

Instead of passing several values from an object as parameters to a method, pass the whole object to allow the method to access more data if needed in the future.

java
    public class Order {
        private double price;
        private String customerName;
        private String deliveryAddress;

        // Getters and setters
    }

    public void processOrder(Order order) {
        double price = order.getPrice();
        String customerName = order.getCustomerName();
        String deliveryAddress = order.getDeliveryAddress();

        // Instead, pass the entire order object
        sendConfirmationEmail(order);
    }

    public void sendConfirmationEmail(Order order) {
        // Access order properties as needed
    }

9. Replace Delegation with Inheritance

If you are delegating all methods of a class to another, consider using inheritance to simplify the design.

java
    public class Printer {
        public void print(String text) {
            System.out.println(text);
        }
    }

    public class AdvancedPrinter extends Printer {
        // Instead of delegating, inherit the print method
    }

10. Replace Inheritance with Delegation

If a subclass only uses part of the superclass interface or does not want to inherit the superclass's data, use delegation instead of inheritance.

java
    public class Engine {
        public void start() {
            System.out.println("Engine started");
        }
    }

    public class Car {
        private Engine engine;

        public Car(Engine engine) {
            this.engine = engine;
        }

        public void start() {
            engine.start(); // Delegate to the engine
        }
    }

Refactoring in Action: A Simple Example

Let's say you have a class that calculates the area of different shapes:

java
public class AreaCalculator {

    public double calculateArea(String shape, double... dimensions) {
        if (shape.equals("circle")) {
            double radius = dimensions[0];
            return Math.PI * radius * radius;
        } else if (shape.equals("rectangle")) {
            double length = dimensions[0];
            double width = dimensions[1];
            return length * width;
        } else {
            throw new IllegalArgumentException("Shape not supported");
        }
    }
}

This class violates the Open/Closed Principle. To add a new shape, you have to modify the class. Let's refactor it using polymorphism:

java
public interface Shape {
    double area();
}

public class Circle implements Shape {
    private double radius;

    public Circle(double radius) {
        this.radius = radius;
    }

    @Override
    public double area() {
        return Math.PI * radius * radius;
    }
}

public class Rectangle implements Shape {
    private double length;
    private double width;

    public Rectangle(double length, double width) {
        this.length = length;
        this.width = width;
    }

    @Override
    public double area() {
        return length * width;
    }
}

public class AreaCalculator {
    public double calculateArea(Shape shape) {
        return shape.area();
    }
}

Now, adding a new shape is as simple as creating a new class that implements the Shape interface. No modification to the existing code is needed.

Integrating Refactoring into Your Workflow

  • Small Steps: Refactor in small, incremental steps. This makes it easier to catch errors and reduces the risk of breaking things.
  • Test-Driven Development: Write tests before you refactor. This ensures that your changes don't break existing functionality.
  • Code Reviews: Get feedback from your peers. Fresh eyes can spot code smells and suggest better solutions.
  • Continuous Integration: Integrate refactoring into your CI/CD pipeline. This helps you catch issues early and often.

Where Coudo AI Comes In

Here at Coudo AI, you can find a range of problems like snake-and-ladders or expense-sharing-application-splitwise. While these might sound like typical coding tests, they encourage you to map out design details too. And if you’re feeling extra motivated, you can try Design Patterns problems for deeper clarity.

One of my favourite features is the AI-powered feedback. It’s a neat concept. Once you pass the initial test cases, the AI dives into the style and structure of your code. It points out if your class design could be improved.

FAQs

1. How often should I refactor?

Refactor as often as needed. A good rule of thumb is to refactor whenever you touch a piece of code.

2. Is refactoring risky?

Refactoring can be risky if not done carefully. Always write tests before refactoring and refactor in small, incremental steps.

3. What are some good resources for learning more about refactoring?

  • "Refactoring: Improving the Design of Existing Code" by Martin Fowler
  • "Clean Code: A Handbook of Agile Software Craftsmanship" by Robert C. Martin

Closing Thoughts

Refactoring is not just about making your code look pretty. It's about improving the underlying design, making it easier to understand, maintain, and extend. It’s a continuous process that should be integrated into your daily workflow.

So, next time you’re staring at a messy piece of code, don’t despair. Embrace the power of refactoring and transform it into a masterpiece of low-level design. If you’re curious to get hands-on practice, try Coudo AI problems now. Coudo AI offer problems that push you to think big and then zoom in, which is a great way to sharpen both skills. Remember, it’s easy to get lost in the big picture and forget the details, or vice versa. But when you master both, you create applications that stand the test of time.\n\n

About the Author

S

Shivam Chauhan

Sharing insights about system design and coding practices.