Key Differences Between Inheritance and Polymorphism
Updated on Mar 06, 2025 | 21 min read | 19.2k views
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Updated on Mar 06, 2025 | 21 min read | 19.2k views
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Java Object-oriented programming represents a fundamental approach to software development, offering powerful mechanisms for code organization and reuse. Inheritance and polymorphism are important concepts in Java programming shaping how developers structure and interact with code.
Knowing the difference between inheritance and polymorphism goes beyond their technical implementation. Inheritance allows code reuse and establishes hierarchical relationships, while polymorphism introduces dynamic behavior and flexible method implementations. Together, they form the backbone of advanced object-oriented programming strategies.
Inheritance and polymorphism provide strategic tools in Java for creating flexible, maintainable code structures. These concepts enable programmers to build sophisticated software architectures that adapt to changing requirements. Developers must recognize these concepts as interconnected strategies for solving complex programming challenges. The following article will help you learn everything about polymorphism vs inheritance in Java and their practical applications in modern software engineering.
Inheritance is a feature of object-oriented programming (OOP) in Java that lets one class receive properties and behaviors from another class. This concept forms a base for code reusability in Java and creates links between classes in a parent-child structure. Here, the child refers to the Subclass that inherits properties from the Superclass or parent. Let us explore the features of Inheritance in detail:
Java inheritance works through a system where child classes are built on parent classes. The keyword 'extends' establishes this inheritance relationship in Java. When one class extends another, it gets access to the fields and methods of the parent class by forming an IS-A relationship. You can refer to upGrad’s Inheritance in Java Tutorial for an in-depth understanding of its core functions.
A child class receives these elements from its parent in the following three methods:
Java allows single inheritance for classes. This means one class can extend only one parent class. This rule keeps the code clear and stops complex problems that come with multiple parent classes. Here are the main types of inheritance in Java:
Though Java blocks direct multiple inheritance, a class can implement many interfaces. Each interface adds a contract of methods the class must create. This approach gives the benefits of multiple inheritance while avoiding its problems.
For example, a Car class extends Vehicle but can also implement interfaces like Insurable and Maintainable. This structure allows the Car class to inherit core vehicle features from its parent and add specific behaviors through interfaces.
The interface system creates a clean way to add features to classes. It helps write code that others can understand and change. This plays an important role in big projects where many programmers and teams work together.
The Vehicle hierarchy shows how inheritance works in practice. This structure matches real-world relationships between objects. A basic example shows these connections:
class Vehicle { String brand, model; void move() }
class Car extends Vehicle { int numberOfDoors; void switchGear() }
class SportsCar extends Car { void turboBoost() }
This structure creates clean, organized code. It puts shared features in parent classes and specific features in child classes. This setup makes the code easy to fix and grow over time.
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Polymorphism means "many forms" and represents a core concept in Java where objects behave differently based on their context. It lets you write code that works with objects of a parent class but responds correctly when you use objects of any child class. This creates flexibility in programs and makes code more reusable. Let us discuss the core features of Polymorphism in Java in detail:
Polymorphism in Java happens in two ways: at runtime through method overriding and at compile time through method overloading. These mechanisms serve different purposes and work at different stages of program execution.
Method overriding occurs when a child class changes the behavior of a parent class method. The program decides which version of the method to use based on the actual object type when the program runs. Method overloading happens when you create multiple methods with the same name but different parameters. The compiler figures out which method to call based on the parameters you provide.
The table below lists the key distinguishing features between the two types of Polymorphism in Java:
Feature |
Runtime (Overriding) |
Compile-time (Overloading) |
When it happens |
During program execution |
During code compilation |
How it works |
Uses inheritance |
Works in the same class |
Method signature |
Must stay the same |
Must be different |
Return type |
Must match or be a subtype |
Can be different |
Parameters |
Must match exactly |
Must differ in type or number |
Dynamic method dispatch forms the heart of runtime polymorphism in Java. It is a process in Java that helps decide which method to call at runtime. The Java Virtual Machine (JVM) picks the right method version based on the actual object type, not the reference type. When you call a method, Java follows these steps:
For example:
Animal myPet = new Dog();
myPet.makeSound();
Here, even though the reference type is Animal, the program calls Dog's makeSound method. This happens because Java checks the actual object type (Dog) at runtime and uses its method implementation.
Polymorphism helps you create flexible, maintainable code that can handle different types of objects without major changes. Consider a shape-drawing program:
public interface Shape {
double calculateArea();
void draw();
}
public class Circle implements Shape {
private double radius;
public double calculateArea() {
return Math.PI * radius * radius;
}
public void draw() {
}
}
Here, this structure shows interface-driven flexibility and provides several benefits:
This can be applied to a real application to:
This approach makes the code more maintainable and easier to extend with new features.
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Inheritance and polymorphism work together but serve different purposes in object-oriented programming. Inheritance creates relationships between classes to share code. Polymorphism builds on these relationships to make programs more flexible. Together, they form building blocks for writing organized, adaptable code. Let us discuss the key differences between Inheritance and Polymorphism in detail:
Inheritance builds structured relationships where classes share characteristics. For example, a dog class inherits from an Animal class because a dog is an animal. Each child class extends its parent's features.
Polymorphism allows objects to change their behaviour based on their specific type. When different dogs make different sounds, this shows polymorphism at work. The same method call produces different results.
These concepts establish different kinds of connections in Java programs. The table below lists the relationship types features in polymorphism vs inheritance :
Feature |
Inheritance |
Polymorphism |
Nature |
Creates parent-child class hierarchies |
Enables objects to take multiple forms |
Direction |
Moves from parent to child class |
Works across class hierarchies |
Structure |
Forms IS-A relationship |
Creates behavior variations |
Scope |
Shares code between related classes |
Changes behavior based on context |
Inheritance uses the ‘extends’ keyword to create class relationships, whereas Polymorphism uses method overriding (@override), dynamic binding (real-time decision-making process), and interfaces. The way we write code for these concepts differs with keywords and mechanisms. The table below lists the key differences between Inheritance and Polymorphism based on implementation techniques:
Feature |
Inheritance |
Polymorphism |
Keywords |
extends, super |
@Override annotation |
Mechanism |
Class extension |
Method overriding, interfaces, and dynamic binding in Java |
Time |
Set at class creation |
Happens during execution |
Focus |
Code organization |
Behavior flexibility |
Inheritance provides the structure, while polymorphism adds flexibility to that structure. Choosing when to use each makes programs more organized and adaptable. Each concept serves distinct purposes in programming but complements each other when used correctly. The table below lists the key differences between Inheritance and Polymorphism based on their primary use cases:
Purpose |
Inheritance |
Polymorphism |
Main Goal |
Code reuse |
Flexibility |
Problem Solved |
Duplicate code |
Rigid behavior |
Design Impact |
Class organization |
Interface design |
Scale |
Class Level |
Method level |
Inheritance works best when:
Polymorphism is useful when:
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The choice between Polymorphism and Inheritance shapes how your program grows and adapts. Each option fits different situations and solves different problems. Knowing when to use each one helps create better programs. Using inheritance is like building family trees of classes, while polymorphism creates flexible behaviors that change based on context. Together, they create powerful solutions. Let us discuss their use cases in detail:
Inheritance works best when you see clear parent-child relationships in your program design. Take an example of how living things relate to each other in nature. A bird is a type of animal, and a sparrow is a type of bird. Use inheritance when you find:
Consider choosing inheritance for:
Polymorphism creates flexibility in your programs. It lets different objects respond to the same message in their own ways. This fits situations where behavior needs to change based on the specific type of object. Polymorphism enables effective software design strategies across multiple scenarios:
1. Code Decoupling
Code decoupling breaks dependencies between software components by separating what a component does (its interface) from its implementation. This makes systems more flexible and maintainable. Polymorphism in code decoupling:
2. Plugin Architectures
Plugin architectures create systems that can be extended with new features without changing the core code. Here, Polymorphism performs the following functions:
3. Dynamic Behavior Changes
Dynamic behavior changes let a program modify how objects behave while it is running. It helps in choosing which code to execute based on the current situation rather than having fixed behaviors set during development. Polymorphism enables dynamic behavior changes as it:
Polymorphism converts rigid software structures into dynamic, adaptable systems that can evolve with changing requirements.
Despite the difference between inheritance and Polymorphism, they work together to create flexible, organized code. Here is how you can combine them effectively:
Step 1: Start with inheritance to build your class structure:
Step 2: Add polymorphic behavior:
Consider the sample code for combining:
abstract class Vehicle {
abstract void move(); // Polymorphic method
void startEngine() { // Inherited method
// Common engine start code
}
}
class Car extends Vehicle {
@Override
void move() {
// Car-specific movement
}
}
class Boat extends Vehicle {
@Override
void move() {
// Boat-specific movement
}
}
This combination of Inheritance and Polymorphism in a Java code provides:
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Developers face several technical challenges when building software systems. Many of these challenges come from misusing core programming concepts like inheritance and polymorphism. You can refer to our OOPS Concept in Java Tutorial to learn the basics and avoid common mistakes. Mitigating these mistakes helps create better code that lasts longer and works well. Let us discuss these in detail:
Many developers create deep inheritance hierarchies thinking they save code. This creates problems when programs need to change. Each layer of inheritance makes the code harder to understand and more likely to break. For example, consider this hierarchy:
class Animal
class Mammal extends Animal
class Carnivore extends Mammal
class BigCat extends Carnivore
class Lion extends BigCat
This structure causes several issues:
Instead, use composition. Composition involves building complex objects by combining simpler ones rather than relying solely on subclassing. This method allows for greater flexibility and adaptability, as new behaviours can be added without modifying existing classes.
Break features into smaller parts that work together as given in the code sample given below:
class Lion {
private Movement movement;
private Hunting hunting;
private Sound sound;
}
This approach:
Developers often mix up the two main types of polymorphism in Java, which leads to code that does not work as intended. The knowledge of the difference between compile-time and runtime polymorphism helps prevent these issues. Key misunderstanding areas:
Method overloading in Java (compile-time polymorphism) creates multiple methods with the same name but different parameters. The compiler decides which method to call based on the parameters you provide. Consider this example:
class Calculator {
int add(int a, int b) {
return a + b;
}
double add(double a, double b) {
return a + b;
}
}
On the other hand, Method overriding in Java (runtime polymorphism) happens when a child class changes the behavior of a parent class method. The program decides which version to use when it runs. For example:
class Animal {
String makeSound() {
return "Generic sound";
}
}
class Dog extends Animal {
@Override
String makeSound() {
return "Woof";
}
}
To avoid confusion:
Java allows a class to extend only one parent class, and this limit exists for good reasons. It prevents complex inheritance trees that cause problems in languages with multiple inheritance. However, this limitation can be restrictive for developers who want to build complex systems with shared behaviors. Ignoring this restriction can lead to convoluted class hierarchies and make code more difficult to understand and maintain.
However, interfaces provide a way to gain multiple-inheritance-like benefits without the drawbacks. This approach provides the flexibility needed to build robust systems. Consider this approach:
interface Swimmer {
void swim();
}
interface Flyer {
void fly();
}
class Bird extends Animal implements Flyer {
public void fly() {
// Flying implementation
}
}
class Duck extends Bird implements Swimmer {
public void swim() {
// Swimming implementation
}
}
This design offers several advantages:
To work effectively with Java's inheritance limit:
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Developers face several technical challenges when building software systems. Many of these challenges come from misusing core programming concepts like inheritance and polymorphism. You can refer to our OOPS Concept in Java Tutorial to learn the basics and avoid common mistakes. Mitigating these mistakes helps create better code that lasts longer and works well. Let us discuss these in detail:
Many developers create deep inheritance hierarchies thinking they save code. This creates problems when programs need to change. Each layer of inheritance makes the code harder to understand and more likely to break. For example, consider this hierarchy:
class Animal
class Mammal extends Animal
class Carnivore extends Mammal
class BigCat extends Carnivore
class Lion extends BigCat
This structure causes several issues:
Instead, use composition. Composition involves building complex objects by combining simpler ones rather than relying solely on subclassing. This method allows for greater flexibility and adaptability, as new behaviours can be added without modifying existing classes.
Break features into smaller parts that work together as given in the code sample given below:
class Lion {
private Movement movement;
private Hunting hunting;
private Sound sound;
}
This approach:
Developers often mix up the two main types of polymorphism in Java, which leads to code that does not work as intended. The knowledge of the difference between compile-time and runtime polymorphism helps prevent these issues. Key misunderstanding areas:
Method overloading in Java (compile-time polymorphism) creates multiple methods with the same name but different parameters. The compiler decides which method to call based on the parameters you provide. Consider this example:
class Calculator {
int add(int a, int b) {
return a + b;
}
double add(double a, double b) {
return a + b;
}
}
On the other hand, Method overriding in Java (runtime polymorphism) happens when a child class changes the behavior of a parent class method. The program decides which version to use when it runs. For example:
class Animal {
String makeSound() {
return "Generic sound";
}
}
class Dog extends Animal {
@Override
String makeSound() {
return "Woof";
}
}
To avoid confusion:
Java allows a class to extend only one parent class, and this limit exists for good reasons. It prevents complex inheritance trees that cause problems in languages with multiple inheritance. However, this limitation can be restrictive for developers who want to build complex systems with shared behaviors. Ignoring this restriction can lead to convoluted class hierarchies and make code more difficult to understand and maintain.
However, interfaces provide a way to gain multiple-inheritance-like benefits without the drawbacks. This approach provides the flexibility needed to build robust systems. Consider this approach:
interface Swimmer {
void swim();
}
interface Flyer {
void fly();
}
class Bird extends Animal implements Flyer {
public void fly() {
// Flying implementation
}
}
class Duck extends Bird implements Swimmer {
public void swim() {
// Swimming implementation
}
}
This design offers several advantages:
To work effectively with Java's inheritance limit:
Java's object-oriented programming continues to grow with features that make code clearer and more powerful. In 2025, enhanced patterns and JVM optimization features of Java OOP will help developers write safer code with fewer errors. These changes build on Java's core strengths while adding new ways to express program designs.
Pattern matching helps developers check object types and extract information efficiently. It simplifies complex type-checking and conversion processes in object-oriented programming. Java introduces sophisticated mechanisms to handle type comparisons and transformations. The system allows developers to write more concise and readable code when working with different object types. Key Characteristics are:
Sealed classes restrict inheritance hierarchies. They control which classes can extend a base class. This approach:
Pattern matching streamlines polymorphic designs. This feature with sealed classes creates:
Records represent lightweight data containers with built-in immutability. They simplify data management while maintaining core object-oriented principles. Since records are immutable, once you create an instance of a record, the data it holds cannot change. This property provides clarity and ensures data integrity, making records a reliable choice when representing fixed data. The characteristics of records are:
A significant aspect of records is their approach to inheritance. Records cannot extend to other classes, which ensures that they remain simple and focused solely on data representation. However, records can implement interfaces. This flexibility allows developers to define behavior that records can adopt without complicating their structure with traditional class inheritance. By favoring composition over inheritance, records encourage a design that prioritizes simplicity and maintainability.
The integration of records into OOP in Java emphasizes the principles of immutability and data integrity. Developers can handle data safely and in a type-consistent manner, reducing errors.
The Java Virtual Machine (JVM) optimizes code execution in Java OOP. Just-In-Time (JIT) compilation transforms Java bytecode into machine-specific instructions dynamically. This process happens during program runtime, enabling significant performance improvements. The JIT compiler uses the following techniques:
The JVM uses these intelligent techniques to optimize polymorphic method calls. It creates specialized machine code for frequently executed methods. This approach eliminates repetitive type-checking and method resolution steps. The system learns from runtime behavior, creating optimized execution paths.
Modern JVMs implement advanced inline caching mechanisms. These techniques remember previous method call types and generate specialized code. When similar method calls occur, the JVM reuses optimized machine instructions, significantly reducing computational overhead.
These optimizations help Java evolve from an interpreted language to a highly performant platform. The JVM adapts to specific hardware configurations, generating machine-specific instructions that run efficiently.
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upGrad’s course modules combine classroom learning with hands-on experience by teaching students how to Code, Compile, and Run Java Projects. Completing these upskilling programs shows employers that you can apply OOP principles to solve complex programming challenges. The certification acts as a trusted credential, helping you stand out in competitive job markets.
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The future of Java object-oriented programming lies at the intersection of innovation and practical implementation. Inheritance and polymorphism continue to develop, responding to emerging software development challenges. Developers must understand the difference between inheritance and Polymorphism to understand their unique strengths and how they complement each other in Java programming.
In 2025, Machine learning and artificial intelligence integration will reshape how developers approach object-oriented design. These technologies demand more dynamic, flexible code structures. Inheritance and polymorphism will serve as foundational mechanisms for creating adaptive software systems. Effective use of these concepts enables the creation of software that is scalable and responsive to changing business requirements.
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Reference Links:
https://oopjavavit.blogspot.com/2012/03/dynamic-method-dispatch.html
https://www.tpointtech.com/inheritance-in-java
https://www.w3schools.com/java/java_inheritance.asp
https://www.tpointtech.com/types-of-inheritance-in-java
https://github.com/RameshMF/object-oriented-design/blob/master/oops-concepts/src/main/java/com/ramesh/ood/concepts/polymorphism/Polymorphism.java
https://www.slideshare.net/slideshow/javapolymorphism-217156116/217156116
https://www.reddit.com/r/learnprogramming/comments/17ug404/god_polymorphism_in_java/
https://www.oracle.com/java/technologies/javase/17-relnote-issues.html
https://www.baeldung.com/java-17-new-features
https://www.youtube.com/watch?v=aKaw9W789wU
https://www.infoq.com/articles/pattern-matching-for-switch/
https://github.com/jversed/Lesson07_inheritance
https://gist.github.com/testerlawrence/8b3f77287c8b4d11dc21875dc40b3d36
https://www.quora.com/What-is-polymorphism-and-how-would-you-implement-it-in-Java
https://stackoverflow.com/questions/6308178/what-is-the-main-difference-between-inheritance-and-polymorphism
https://www.alexomegapy.com/post/inheritance-and-polymorphism-in-java-using-superclasses-and-subclasses
https://github.com/realm/realm-java/issues/761
https://nus-cs2030.github.io/1718-s2/lec02/index.html
https://www.quora.com/What-is-the-relationship-between-inheritance-and-polymorphism
https://www.quora.com/Is-it-possible-to-implement-inheritance-without-polymorphism-in-Java
https://www.tpointtech.com/runtime-polymorphism-in-java
https://www.youtube.com/watch?v=DWpYniQAVyI
https://techaffinity.com/blog/oops-concepts-in-java/
https://www.researchgate.net/publication/234781793_Difficulties_in_Learning_Inheritance_and_Polymorphism
https://www.reddit.com/r/cpp/comments/pemngr/common_patterns_to_avoid_polymorphism/
https://30dayscoding.com/blog/disadvantages-of-inheritance-in-java
https://beginnersbook.com/2024/12/common-errors-in-inheritance-in-java-examples-and-solutions/
https://javanexus.com/blog/mastering-java-oop-inheritance-mistakes
https://kindsonthegenius.com/blog/encapsulation-inheritance-and-polymorphism-in-object-oriented-programming/
https://www.techelevator.com/the-3-pillars-of-object-oriented-programming-oop-brought-down-to-earth/
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