Make your class hierarchy clear and flexible TL;DR: Extract a common abstract class to mimic real-world structure. Problems Addressed Duplicate Code
Inappropriate Inheritance
Shotgun Surgery
Big Class
Feature Envy
High Coupling
Concrete classes subclassified
Parent class not abstract Related Code Smells https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiv?embedable=true https://hackernoon.com/code-smell-255-addressing-parallel-hierarchies-in-code?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiii?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-ix-7rr33ol?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxxiii?embedable=true Steps Identify common behaviors in both classes.


Create an abstract class with shared behavior and no implementation.


Move common logic to the abstract class.


Update subclasses to inherit from the abstract class. Sample Code Before class Car {
    void drive() {
        System.out.println("Driving a car");
    }
}

class Truck extends Car {
    void load() {
        System.out.println("Loading cargo");
    }

    void unload() {
        System.out.println("Unloading cargo");
    }
}

// Truck reuses driving method
// Overriding it would be another code smell
// Violating Liskov Substitution rule After abstract class Vehicle {
    // 2. Create an abstract class
    // with shared behavior and no implementation
    abstract void drive();
    // 1. Identify common behaviors in both classes
    // 3. Move common logic to the abstract class
}

class Car extends Vehicle {
    // 4. Update subclasses to inherit from the abstract class
    void drive() {
        System.out.println("Driving a car");
    }
}

class Truck extends Vehicle {
    // 4. Update subclasses to inherit from the abstract class
    void drive() {
        System.out.println("Driving a truck");
        // Implementation is different than the car's
    }

    void load() {
        System.out.println("Loading cargo");
    }

    void unload() {
        System.out.println("Unloading cargo");
    }
} Type [x]Semi-Automatic Safety This refactoring is safe if you identify all common behaviors correctly and move one method at a time running the tests. Why is the Code Better? It reduces duplication, simplifies maintenance, and makes it easier to extend functionality by adding new concrete realizations. How Does it Improve the Bijection? By introducing an abstract class, the code better reflects the real-world hierarchy, creating a clear relationship between the generic and specific types. Refactor with AI Without Proper Instructions

With Specific Instructions



ChatGPT

ChatGPT



Claude

Claude



Perplexity

Perplexity



Copilot

Copilot



Gemini

Gemini



Meta AI

Meta AI Tags Inheritance Related Refactorings https://hackernoon.com/refactoring-013-eliminating-repeated-code-with-dry-principles?embedable=true See also https://refactoring.guru/es/extract-superclass?embedable=true Credits Image by Pexels on Pixabay This article is part of the Refactoring Series. https://maximilianocontieri.com/how-to-improve-your-code-with-easy-refactorings?embedable=true Make your class hierarchy clear and flexible Make your class hierarchy clear and flexible TL;DR: Extract a common abstract class to mimic real-world structure. TL;DR: Extract a common abstract class to mimic real-world structure. Problems Addressed Duplicate Code Inappropriate Inheritance Shotgun Surgery Big Class Feature Envy High Coupling Concrete classes subclassified Parent class not abstract Duplicate Code Duplicate Code Inappropriate Inheritance Shotgun Surgery Shotgun Surgery Big Class Feature Envy Feature Envy High Coupling Concrete classes subclassified Concrete classes subclassified Parent class not abstract not abstract Related Code Smells https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiv?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiv?embedable=true https://hackernoon.com/code-smell-255-addressing-parallel-hierarchies-in-code?embedable=true https://hackernoon.com/code-smell-255-addressing-parallel-hierarchies-in-code?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiii?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xiii?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-ix-7rr33ol?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-ix-7rr33ol?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxxiii?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxxiii?embedable=true Steps Identify common behaviors in both classes. Create an abstract class with shared behavior and no implementation. Move common logic to the abstract class. Update subclasses to inherit from the abstract class. Identify common behaviors in both classes. Identify common behaviors in both classes. Create an abstract class with shared behavior and no implementation. Create an abstract class with shared behavior and no implementation. Move common logic to the abstract class. Move common logic to the abstract class. Update subclasses to inherit from the abstract class. Update subclasses to inherit from the abstract class. Sample Code Before class Car {
    void drive() {
        System.out.println("Driving a car");
    }
}

class Truck extends Car {
    void load() {
        System.out.println("Loading cargo");
    }

    void unload() {
        System.out.println("Unloading cargo");
    }
}

// Truck reuses driving method
// Overriding it would be another code smell
// Violating Liskov Substitution rule class Car {
    void drive() {
        System.out.println("Driving a car");
    }
}

class Truck extends Car {
    void load() {
        System.out.println("Loading cargo");
    }

    void unload() {
        System.out.println("Unloading cargo");
    }
}

// Truck reuses driving method
// Overriding it would be another code smell
// Violating Liskov Substitution rule After abstract class Vehicle {
    // 2. Create an abstract class
    // with shared behavior and no implementation
    abstract void drive();
    // 1. Identify common behaviors in both classes
    // 3. Move common logic to the abstract class
}

class Car extends Vehicle {
    // 4. Update subclasses to inherit from the abstract class
    void drive() {
        System.out.println("Driving a car");
    }
}

class Truck extends Vehicle {
    // 4. Update subclasses to inherit from the abstract class
    void drive() {
        System.out.println("Driving a truck");
        // Implementation is different than the car's
    }

    void load() {
        System.out.println("Loading cargo");
    }

    void unload() {
        System.out.println("Unloading cargo");
    }
} abstract class Vehicle {
    // 2. Create an abstract class
    // with shared behavior and no implementation
    abstract void drive();
    // 1. Identify common behaviors in both classes
    // 3. Move common logic to the abstract class
}

class Car extends Vehicle {
    // 4. Update subclasses to inherit from the abstract class
    void drive() {
        System.out.println("Driving a car");
    }
}

class Truck extends Vehicle {
    // 4. Update subclasses to inherit from the abstract class
    void drive() {
        System.out.println("Driving a truck");
        // Implementation is different than the car's
    }

    void load() {
        System.out.println("Loading cargo");
    }

    void unload() {
        System.out.println("Unloading cargo");
    }
} Type [x]Semi-Automatic [x] Semi-Automatic [x] Safety This refactoring is safe if you identify all common behaviors correctly and move one method at a time running the tests. Why is the Code Better? It reduces duplication, simplifies maintenance, and makes it easier to extend functionality by adding new concrete realizations. How Does it Improve the Bijection? By introducing an abstract class, the code better reflects the real-world hierarchy, creating a clear relationship between the generic and specific types. real-world Refactor with AI Without Proper Instructions

With Specific Instructions



ChatGPT

ChatGPT



Claude

Claude



Perplexity

Perplexity



Copilot

Copilot



Gemini

Gemini



Meta AI

Meta AI Without Proper Instructions

With Specific Instructions ChatGPT

ChatGPT Claude

Claude Perplexity

Perplexity Copilot

Copilot Gemini

Gemini Meta AI

Meta AI Without Proper Instructions With Specific Instructions Without Proper Instructions Without Proper Instructions With Specific Instructions With Specific Instructions ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT Claude Claude Claude Claude Claude Claude Claude Claude Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Copilot Copilot Copilot Copilot Copilot Copilot Copilot Copilot Gemini Gemini Gemini Gemini Gemini Gemini Gemini Gemini Meta AI Meta AI Meta AI Meta AI Meta AI Meta AI Meta AI Meta AI Tags Inheritance Inheritance Related Refactorings https://hackernoon.com/refactoring-013-eliminating-repeated-code-with-dry-principles?embedable=true https://hackernoon.com/refactoring-013-eliminating-repeated-code-with-dry-principles?embedable=true See also https://refactoring.guru/es/extract-superclass?embedable=true https://refactoring.guru/es/extract-superclass?embedable=true Credits Image by Pexels on Pixabay Pexels Pixabay This article is part of the Refactoring Series. https://maximilianocontieri.com/how-to-improve-your-code-with-easy-refactorings?embedable=true https://maximilianocontieri.com/how-to-improve-your-code-with-easy-refactorings?embedable=true

Refactoring 022 - Extract Common Ancestor

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