Inheritance in Object-Oriented Programming (OOP)

Inheritance is a core concept of object-oriented programming that facilitates code reusability and organization. Understanding inheritance will help you become an overall better programmer and help you take your own projects to the next level. In this blog, we will explore inheritance in OOP with examples in the most popular programming languages.

Table of Contents:

• Introduction to Inheritance in OOP
• Real-Life Examples of Inheritance
• Types of Inheritance in OOP
• Summary of Types of Inheritance in OOP
• Syntax of Inheritance in Different Languages
• Access Modifiers and Their Role in Inheritance
• Method Overriding in Inheritance
• Benefits of Using Inheritance
• Common Mistakes and Best Practices
• Inheritance vs Composition
• Conclusion

Introduction to Inheritance in OOP

Inheritance is the programming design mechanism that allows one class (child class) to inherit the properties and behavior of another class (parent/superclass). This helps your code become reusable and makes your application more scalable. It essentially provides a workaround for writing the same code over and over again for different classes.

Let’s say, for example, you have specific classes like bike, car, truck, etc. These classes would have similar functionality and methods that you may want to call. You can create a parent class called vehicle to hold these methods, such as openTrunk() for a car or loadCargo() for trucks, etc., instead of rewriting the code for each class.

Real-Life Examples of Inheritance

Let’s explore some real-life examples of inheritance in OOP, which is the best way to learn any programming concept. 

Family Tree Example

Think of a family tree where:

• Grandparent has certain traits (e.g., eye color, blood type)
• Parent inherits those traits and add some of their own
• A child inherits from their parents and can still access their grandparents’ traits

In OOP terms:

• Grandparent is the base class
• Parent is the intermediate subclass
• Child is a derived subclass that inherits all features up the chain

This is an example of multilevel inheritance.

UI Components Example

In GUI libraries or frontend frameworks:

• A base class like Component defines core behavior like rendering or updating the screen.
• Specialized classes like Button, Checkbox, or Dropdown inherit from Component and add specific behavior.

This real-world use of inheritance helps maintain a consistent interface and behavior across all UI elements.

Types of Inheritance in OOP

The inheritance types in OOP are based on the relationship between the parent and child classes. The better you understand the behavior of each type and the definition of inheritance in OOP, the better you will be able to apply it in your own code.

1. Single Inheritance

In single inheritance, the child class only has access to the methods and behaviour of one parent class.

Example(Python):

Output:

The animal makes a sound

This is the most common and simple form of inheritance in OOP. It keeps the class hierarchy simple and easy to understand, making it ideal for smaller systems or when only one source of shared behavior is needed.

2. Multiple Inheritance in OOP

Multiple inheritance, as the name implies, is when a child class inherits the behavior and functionality of one or more parent classes.

Example(Python)

Output:

Father's skill: Gardening

It allows you to combine diverse behaviors from multiple sources into a single class, which is ideal when modeling real-world roles or traits that come from different origins.

Note: Not supported in Java directly due to ambiguity (known as the diamond problem).

3. Multilevel Inheritance

Multilevel inheritance takes it a step further, where a class is derived from a subclass, which itself is derived from another class, like the family tree analogy that we used previously.

Example(C++):

Output:

Animal makes a sound
Dog barks
Puppy weeps

This structure is useful for building layered, hierarchical relationships where each level adds specialized behavior. It mirrors real-life inheritance chains and supports code refinement over time.

4. Hierarchical Inheritance

Multiple classes inherit from a single base class.

Example(Java):

Output:

All animals eat food.
Dog barks.

All animals eat food.
Cat meows.

This type of inheritance in OOP helps organize shared behavior in one place, so that multiple child classes can reuse common logic without duplication.

5. Hybrid Inheritance in OOP

Hybrid Inheritance is a combination of two or more types of inheritance.

Example(Python):

Class D inherits from both B and C, which in turn includes A. This is a hybrid of multilevel and multiple inheritance. Use print(D.__mro__) in Python to inspect method resolution order. This allows flexibility to model complex, real-world systems where different inheritance strategies need to be combined.

Summary of Types of Inheritance in OOP

Syntax of Inheritance in Different Languages

Now, with a solid understanding of the types of inheritance, we can explore real-world scenarios of inheritance in code.

1. Inheritance in Java

In Java, you use the extends keyword to inherit from a class.

Output:

This animal eats food.
The dog barks.

Java supports single, multilevel, and hierarchical inheritance. Multiple inheritance is not supported with classes; interfaces are used instead.

2. Inheritance in Python

Python allows multiple inheritance using parentheses to list base classes.

Output:

The animal is eating.
The dog is barking.

Python supports all five types of inheritance and handles method conflicts using MRO (Method Resolution Order).

3. Inheritance in C++

C++ supports single, multiple, and hybrid inheritance directly using a colon (:) followed by an access specifier.

Output:

Animal eats food
Dog barks

4. Inheritance in C#

In C#, the : symbol is used to inherit from a base class.

Output:

 
Animal eats food.
Dog barks.

Like Java, C# supports only single-class inheritance, and interfaces can be used for multiple inheritance.

Access Modifiers and Their Role in Inheritance

We know that inheritance is used to share functionality among classes, but it is also important to handle access in a logical and scalable way, meaning that all classes do not need access to all methods in the parent class. Access modifiers are used to handle visibility and access to child classes. These modifiers, namely, public, private, protected, and default, determine how accessible a member is to other classes, including subclasses, helping ensure encapsulation and maintainable code.

1. Public

If a class is marked public, it can be accessed from anywhere. This includes inside the class, inside the child class, and even outside the class.

Example(Java):

Output:

Eating...
Barking...

Here, Dog inherits the eat() method from Animal and can use it freely. It’s like a public blog post; everyone can see it.

2. Private

If something is marked private, it stays inside the scope of the class where it is declared. Even child classes derived from that class will not have access.

Example (C++)

Output:

Dog barks
This is private

In this case, secret() is hidden from Dog.

3. Protected

Protected sits between private and public. It’s not accessible from anywhere, but child classes will be able to access it.

Example (C#):

Output:

Sleeping...

4. Default

In Java, if you don’t specify any modifier, it’s only accessible within the same package. So it’s kind of like sharing something within your group of coworkers, but not beyond.

Method Overriding in Inheritance

Using inheritance, child classes can access the methods inside the superclass. But what if the child class needs to change some of the functionality? This is where method overriding comes into the picture.

What is Overriding?

Method overriding allows a subclass to provide a custom implementation of a method that it inherits from its superclass. This is especially useful when you want similar behavior with a specific twist for a particular class

Example(Java)

Output:

Dog barks

super Keyword usage

The super keyword is used when you want to original method from the parent class along with the new behaviour.

Example(Java):

Output:

Some generic animal sound
...but specifically, Dog barks

Preventing Override

In some cases, you might want to stop a method from being overridden. You can do this using keywords like:

• final (Java, C++)
• sealed (C#)

Benefits of Using Inheritance

The use of inheritance in your code makes it cleaner, smarter, and easier to work with. Let’s explore the benefits of using inheritance in detail.

1. Code Reusability

The main reason that inheritance exists is for code reusability. It allows you to define common functionality between child and parent classes. 

Example:

You might have a User class that contains a method login(). Now both Admin and Customer classes can use that method without duplicating code.

This not only saves time but also reduces bugs, because updates to the method need to be made in just one place.

2. Modularity

Inheritance promotes modularity, where each class focuses on a specific functionality while being connected to a larger structure.

Breaking your code into a logical class hierarchy makes it easier to:

• Navigate your codebase 
• Test Individual units
• Identify and fix bugs efficiently

3. Scalability

Inheritance makes it easier to scale your application in the future when the need arises. 

Let’s say you build a system for managing Employees. Later, you need to add support for Contractors and Interns. If they all share behavior from a common Person class, you can scale the system without rewriting everything.

Inheritance supports:

• Adding new features quickly
• Handling complexity with structure
• Keeping your design future-proof

4. Polymorphism support

Polymorphism and inheritance go hand in hand.

When classes share a common parent, you can treat them interchangeably using a reference to the base class and still get the right behavior at runtime.

Example(Java):

Animal a = new Dog();

a.sound();  // Calls Dog’s sound method, not Animal’s

This makes your code more flexible and powerful, especially when working with collections or interfaces.

5. Easier maintenance

Inheritance improves maintainability by centralizing shared logic.

If you need to fix a bug or tweak a method, you do it in the base class, and the change automatically applies to all subclasses. That’s a huge time-saver in larger projects.

It also means fewer chances for errors, less duplicate code, and cleaner updates over time.

Common Mistakes and Best Practices

While inheritance is a powerful tool, it is easy to confuse certain aspects and ruin the implementation. Especially for beginners, it can be a difficult topic to comprehend on the first go. Here are some common mistakes that beginners make when implementing inheritance in their own code.

1. Overuse of Inheritance

Creating multiple levels of inheritance makes the code harder to follow and maintain. Bugs become harder to identify, and a change in a superclass can break things further down the line in a child class.

Best practice: It is recommended that you keep your class hierarchy shallow, 3-4 levels maximum.  If you go further, you should maybe reconsider your class structure.

2. Inheriting Unused Functionality

Subclasses sometimes inherit properties or methods that it does not need. It pollutes the subclass with irrelevant behavior and violates the Single Responsibility Principle.

Best practice: Avoid cramming superclasses with multiple methods and functionality. Follow the Single Responsibility Principle. 

3. Ignoring Access Modifiers

Most beginner developers make everything public, thinking it is more convenient. But in reality, it breaks encapsulation and exposes too much of your class internals to the outside world.

Best practice: Use private for internal logic, protected for subclass access, and public only when absolutely necessary. This keeps your class APIs clean and safe.

4. Forgetting to use super

When overriding methods, some developers forget (or ignore) calling the parent class’s version using super. This can break the expected flow or discard important base functionality.

Best practices: If the base method contains critical logic, always call super.methodName() before or after your custom logic.

Inheritance vs Composition

Both inheritance and composition are powerful ways to reuse code and make your application more scalable. They are designed to solve the same problem but in different ways. Since we already have a fair understanding of what inheritance is, let’s quickly define composition.

Composition creates a “has a” relationship between objects. Instead of inheriting behavior, one class contains an instance of another.

Example:

A Car has an Engine

A Laptop has a Battery

Rather than extending a class, you’re combining different classes to build more complex behavior. Let’s look at the key differences between inheritance and composition:

Conclusion

Inheritance is an important aspect of object-oriented programming. It is widely used by developers to make their applications more scalable and code more reusable. We have already covered all the important aspects of inheritance, such as the definition of inheritance in OOP, types of inheritance, real-world code examples, and more. If you want to dive deeper into object-oriented programming, we highly recommend our OOP in Python tutorial. Or, if you are preparing for a technical interview, check out our top 35+ OOP interview questions.

Inheritance in OOP- FAQs