Difference Between Inheritance and Polymorphism

Difference Between Inheritance and Polymorphism

6 mins readComment
Esha
Esha Gupta
Associate Senior Executive
Updated on Mar 11, 2024 16:47 IST

Have you ever wondered the difference between inheritance and polymorphism in OOP? Inheritance creates class hierarchies for code reuse, while polymorphism enables flexible interactions using shared interfaces. Let's understand more!

Inheritance creates a structured class system based on relationships between general and more specific classes, while polymorphism uses this structure to enable flexible and interchangeable object interactions. Both are crucial for the development of scalable, maintainable, and efficient software, allowing programmers to write clearer, more concise, and more efficient code. In this blog, we will understand the differences between them in detail!

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Table of Content

Difference Between Inheritance and Polymorphism

Below is a table showing the differences between Inheritance and Polymorphism

Aspect

Inheritance

Polymorphism

Definition

Inheritance is a mechanism where a new class is derived from an existing class, inheriting its properties and methods.

Polymorphism allows objects of different classes to be treated as objects of a common super class, primarily through the use of interfaces and abstract classes.

Purpose

Used to achieve reusability of code and establish a relationship between classes (parent-child relationship).

Used to achieve flexibility in code by allowing different classes to be treated as instances of the same class, particularly when their methods share the same name.

How It Works

The child class inherits attributes and behaviors (methods) from the parent class and can also have its own unique attributes and behaviors.

Involves methods that have the same name but may behave differently in different classes. The exact method that gets invoked is determined at runtime.

Types

Single inheritance, multiple inheritance, multilevel inheritance, hierarchical inheritance, hybrid inheritance.

Overloading (compile-time polymorphism) and overriding (runtime polymorphism).

Key Principle

“IS-A” relationship. For example, a Dog is an Animal.

“CAN-DO” relationship. For example, a Printer can print in different ways.

Implementation

Achieved through class definitions. In languages like Java, extends keyword is used.

Achieved through method overloading and overriding. Interfaces or abstract classes are often involved.

Usage Example

A class Car inherits from a class Vehicle. The Car will have all attributes and methods of Vehicle, plus its own unique attributes and methods.

A function draw could be implemented in multiple ways depending on whether it’s drawing a Circle, Square, or Triangle. Each shape will have its own implementation of draw.

Flexibility

It is static and defined at the time of class creation.

It is dynamic and can provide a more flexible interface for interactions between objects.

Limitation

Deep inheritance hierarchies can become complex and hard to manage.

If not properly managed, it can lead to confusion about which method is being called.

 

What is Inheritance?

Inheritance is a fundamental concept in object-oriented programming (OOP). It refers to the mechanism by which one class (referred to as a child class or subclass) acquires the properties (methods and fields) of another class (referred to as a parent class or superclass). 

Key Points About Inheritance

  • Inheritance supports the reuse of existing code. The child class inherits all the public and protected properties and methods from the parent class, facilitating code reuse and reducing redundancy.
  • Through inheritance, new functionality can be added to existing code without altering it. This is particularly useful for adding new features or modifying existing behaviour in an existing class hierarchy.
  • Inheritance allows for polymorphic behaviour where a subclass can be treated as an instance of the parent class. This is fundamental for implementing polymorphism in OOP.
  • It helps in creating a natural hierarchy of classes in a domain. For example, a Vehicle class might be the parent of Car, Truck, and Motorcycle classes.
  • Inheritance allows a child class to override a method defined in its parent class, enabling specific implementations that are different from the parent class.
  • Inheritance is implemented differently in various programming languages. For instance, languages like Java and C# support single inheritance (a class can only inherit from one parent class), while languages like Python and C++ support multiple inheritance (a class can inherit from multiple parent classes). 

What is Polymorphism?

Polymorphism is a core concept in object-oriented programming (OOP) that refers to the ability of different objects to respond in their own way to the same message (or method call). The term "polymorphism" comes from the Greek words "poly" (meaning "many") and "morph" (meaning "form"). In the context of programming, it allows objects of different classes to be treated as objects of a common superclass.

There are two main types of polymorphism in OOP:

1. Compile-Time Polymorphism (or Static Polymorphism): This is achieved through method overloading and operator overloading. It occurs when multiple methods have the same name but differ in parameters (number, type, or both). The correct method to be executed is determined at compile time based on the method signature. For example, in a class, you might have multiple versions of a add() method, each taking different types or numbers of parameters.

2. Run-Time Polymorphism (or Dynamic Polymorphism): This is achieved through method overriding, where a method in a subclass has the same name and type signature as a method in its superclass. The specific version of the method that gets executed is determined at runtime based on the object that is invoking the method. This is typically implemented using a feature called 'inheritance' and interfaces in languages like Java.

Key Points on Polymorphism

  • Polymorphism is often used with interfaces, which define methods that can be implemented by any class. The implementation details are left to the classes that implement these interfaces.
  • It allows for more abstract and generalized coding. The programmer can write code that does not need to be changed when a new subclass is created from a superclass.
  • Code that is written to use an object's interface is flexible and can work with new subclasses that didn't exist when the code was originally written.

Thus,  inheritance and polymorphism are both fundamental concepts in object-oriented programming (OOP). They serve distinct purposes and operate in different ways.

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FAQs

What is inheritance?

Inheritance is a mechanism that allows a new class, known as a subclass or derived class, to take on the properties and behaviors (methods) of another class, referred to as the superclass or base class. It's used to promote code reuse, reduce redundancy, and establish a hierarchical relationship between classes.

What is polymorphism?

Polymorphism is a concept in object-oriented programming that refers to the ability of a single function or method to work in different ways depending on the object it is called on. In other words, it allows objects of different classes to be treated as objects of a common superclass. The most common types of polymorphism are compile-time (or static) polymorphism, which is achieved through method overloading, and runtime (or dynamic) polymorphism, which is achieved through method overriding.

How does inheritance differ from polymorphism?

Inheritance is a structural mechanism that establishes a relationship between classes through which they can share attributes and methods. Polymorphism, on the other hand, is a behavioral mechanism that allows the same operation to behave differently based on the context in which it is used. Essentially, inheritance lets us define relationships between classes, while polymorphism lets us leverage those relationships to affect behavior.

Can you have polymorphism without inheritance?

While polymorphism is most commonly implemented through inheritance, it's not strictly dependent on it. For example, interface implementation in languages like Java also allows polymorphism. Objects of different classes can implement the same interface and be referred to through interface references, allowing for polymorphic behavior without traditional class inheritance. However, inheritance is a common way to achieve polymorphism in many object-oriented languages.

Is one more important than the other?

Inheritance and polymorphism serve different purposes in object-oriented programming and are both important concepts. Inheritance is crucial for defining class hierarchies and for code reuse. Polymorphism, on the other hand, is key to designing flexible and extensible systems that can handle different types of objects through a uniform interface. Both are essential tools in the object-oriented programmer's toolkit, and their importance often depends on the specific problem being solved.

 

 

 

About the Author
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Esha Gupta
Associate Senior Executive

Hello, world! I'm Esha Gupta, your go-to Technical Content Developer focusing on Java, Data Structures and Algorithms, and Front End Development. Alongside these specialities, I have a zest for immersing myself in v... Read Full Bio