Difference Between Overloading and Overriding in Java: Understanding the Key Concepts in 2025
Updated on Dec 31, 2024 | 9 min read | 11.6k views
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Updated on Dec 31, 2024 | 9 min read | 11.6k views
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Have you ever felt stuck trying to figure out why a method behaves one way in one scenario and completely differently in another? If you’re a Java developer or a student exploring Object-Oriented Programming (OOP), understanding this distinction is critical—and it can save you countless hours of debugging.
The key lies in two foundational concepts: overloading and overriding. These mechanisms not only streamline your code but also play a vital role in making it efficient and reusable.
In this blog, we’ll demystify the difference between overloading and overriding in Java with clear explanations and practical examples. By the end, you’ll confidently apply these concepts to write cleaner, more dynamic Java code. Let’s dive in!
Method overloading in Object-Oriented Programming (OOP) allows you to define multiple methods within the same class with the same name but with different parameters. These parameters can vary in terms of their number, type, or order.
Importance of Overloading
Here's a simple code example demonstrating method overloading:
public class Calculator {
public int add(int a, int b) {
return a + b;
}
public int add(int a, int b, int c) {
return a + b + c;
}
public double add(double a, double b) {
return a + b;
}
}
In this example, the add() method is overloaded three times:
Key Characteristics of Method Overloading:
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Also Read: What is Coding? Uses of Coding for Software Engineer in 2024
In the next section, you'll develop a clear understanding of overriding.
Method overriding is a key feature of Object-Oriented Programming that enhances flexibility in code design. It occurs when a subclass redefines a method already declared in its superclass, allowing the subclass to adapt or extend the inherited behavior. This mechanism is crucial for achieving dynamic method dispatch and implementing polymorphism in Java.
Key Characteristics:
Same Method Name and Signature
For overriding to occur, the method in the subclass must have:
For example:
// Parent class
class Animal {
// Method to be overridden
void sound() {
System.out.println("Animal makes a sound");
}
}
// Subclass
class Dog extends Animal {
// Overriding the sound method
@Override
void sound() {
System.out.println("Dog barks");
}
}
public class MethodOverridingExample {
public static void main(String[] args) {
Animal myAnimal = new Animal(); // Create an Animal object
myAnimal.sound(); // Call the method on the Animal object
Animal myDog = new Dog(); // Create a Dog object (reference is Animal)
myDog.sound(); // Call the overridden method on the Dog object
}
}
Occurs Between Two Classes in an Inheritance Relationship
Method overriding is only possible when there is an inheritance relationship between classes. It reflects the "is-a" relationship, where the subclass inherits from the superclass.
For instance:
// Parent class
class Vehicle {
// Method to be overridden
void start() {
System.out.println("Vehicle is starting");
}
}
// Subclass
class Car extends Vehicle {
// Overriding the start method
@Override
void start() {
System.out.println("Car is starting with a key");
}
}
public class MethodOverridingInheritance {
public static void main(String[] args) {
Vehicle myVehicle = new Vehicle(); // Create a Vehicle object
myVehicle.start(); // Calls the start method in Vehicle class
Vehicle myCar = new Car(); // Create a Car object (reference is Vehicle)
myCar.start(); // Calls the overridden start method in Car class
}
}
Role in Runtime Polymorphism:
Method overriding plays a crucial role in achieving runtime polymorphism in OOP. Runtime polymorphism enables you to treat objects of different classes as objects of a common superclass.
Code Example:
class Animal {
public void makeSound() {
System.out.println("Generic animal sound");
}
}
class Dog extends Animal {
@Override
public void makeSound() {
System.out.println("Woof!");
}
}
class Cat extends Animal {
@Override
public void makeSound() {
System.out.println("Meow!");
}
}
public class Main {
public static void main(String[] args) {
Animal animal1 = new Animal();
Animal animal2 = new Dog();
Animal animal3 = new Cat();
animal1.makeSound(); // Output: Generic animal sound
animal2.makeSound(); // Output: Woof!
animal3.makeSound(); // Output: Meow!
}
}
In this example:
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Also Read: Polymorphism in Java: Concepts, Types, Characteristics & Examples
Now, let's explore the essential differences between overloading and overriding in Java.
Overloading and overriding are two fundamental concepts in Java that involve methods with the same name, but they differ in their usage, behavior, and impact. Here's a detailed look at the difference between overloading and overriding.
Feature | Overloading | Overriding |
Definition | Defining multiple methods within the same class with the same name but different parameters. | Providing a specific implementation for a method that is already defined in the superclass. |
Usage | Occurs within the same class. | Occurs between a superclass and its subclass. |
Parameter Requirements | Parameters must differ in terms of number, type, or order. | Parameters must be exactly the same. |
Return Type | Return type can be the same or different. | Return type must be the same or a subtype of the superclass method's return type. |
Access Modifiers | Access modifiers can vary (e.g., public, private, protected). | The access modifier in the subclass cannot be more restrictive than in the superclass. |
Inheritance | No inheritance relationship required. | Requires an "is-a" relationship between the class and the method. |
Polymorphism | Does not directly support runtime polymorphism. | Directly supports runtime polymorphism. |
Method Resolution | Method resolution happens at compile time based on the number, type, and order of arguments. | Method resolution happens at runtime based on the object's actual type. |
Purpose | Primarily used to improve code readability, reduce code duplication, and provide flexibility in method calls. | Primarily used to achieve runtime polymorphism, customize inherited behavior, and extend the functionality of superclass methods. |
Example | add(int a, int b), add(int a, int b, int c), add(double a, double b) | Animal.makeSound(), Dog.makeSound(), Cat.makeSound() |
Static Methods | Can be overloaded. | Cannot be overridden. |
Private Methods | Can be overloaded. | Cannot be overridden. |
Constructors | Can be overloaded. | Cannot be overridden. |
Performance | Generally has minimal impact on performance. | Can have a slight performance overhead due to the dynamic dispatch mechanism. |
Code Reusability | Contributes to code reusability by allowing for a single method name for various scenarios. | Contributes to code reusability by allowing subclasses to reuse and customize superclass functionality. |
Flexibility | Provides flexibility in method calls by allowing different parameter combinations. | Provides flexibility in behavior by allowing subclasses to define their own specific implementations. |
Maintainability | Improves code maintainability by making it easier to read, understand, and modify. | Improves code maintainability by promoting a modular and extensible design. |
Extensibility | Less directly involved in extending class functionality. | Directly supports class extension by allowing subclasses to customize inherited behavior. |
Relationship | No direct relationship between overloading and overriding. | Overriding builds upon the foundation of inheritance. |
Key Concept | Method resolution based on parameter differences. | Runtime polymorphism and dynamic dispatch. |
Developing a deeper understanding about Java OOPS concepts can help you to create scalable and secure applications.
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Choosing between method overloading and overriding depends heavily on your specific design goals and the relationships between classes. Here are some guidelines:
Choose Overloading When:
Choose Overriding When:
Also Read: Encapsulation in Java with Example
Learning about OOP concepts can help you in your software development career. Find out how upGrad can help you with that.
Whether you’re just starting your coding journey or already skilled in languages like Java, Python, or C++, learning Object-Oriented Programming (OOP) is a valuable step. For beginners, it builds a solid foundation in coding principles, and for experienced developers, it opens doors to advanced concepts and lucrative career opportunities.
upGrad provides a variety of software development courses that cover essential concepts like overloading and overriding, empowering you to build efficient and scalable software. Explore these courses to enhance your OOP skills and advance your career:
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