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Polymorphism Power
Overloading, Overriding, and
Real-World Uses
Learning Outcome(Slide2)
5
Apply polymorphism in Java programs
4
Explain method overriding concept
3
Explain method overloading concept
2
Distinguish compile and runtime polymorphism
1
Understand concept of polymorphism
Classes and Objects – How to create objects and use class methods.
Inheritance – How child classes inherit from parent classes.
Methods – How to declare and call methods, with or without parameters.
Compile-time vs Run-time – Difference between decisions made by the compiler and by the program at runtime.
super and this keywords – Calling parent class methods or constructors.
Before Starting ,Lets Recall
Think of a Person
In real life, one person plays different roles in different situations.
He is a father at home, an employee at the workplace, and a customer in a shop.
Although the person remains the same,
their behavior changes based on the role and situation.
In the same way, in Java programming,
an object can take different forms and perform different behaviors when it is used in different contexts.
Even though the reference remains the same,
the actual behavior depends on the object it refers to at runtime.
This concept—where the same method call results in different actions—is known as polymorphism in Java.
Polymorphism means “many forms.”
- One method name, but different behaviors.
- The same action works differently for different objects.
What is Polymorphism in Java?
class Animal {
void sound() {
System.out.println("Animal makes sound");
}
}
class Dog extends Animal {
void sound() {
System.out.println("Dog barks");
}
}
public class Main {
public static void main(String[] args) {
Animal a = new Dog(); // Polymorphism
a.sound(); // Dog barks
}
}
Example
Method Overloading
Compile-Time Polymorphism
Static binding
When: Decision made by compiler at compile time
Rule: Same method name, different parameters.
Logic: The compiler picks the method based on arguments passed
Types of Polymorphism
class Baker{
void bake(){
System.out.println("Basic cake");
}
void bake(String flavor){
System.out.println("Baking "+flavor);
}
void bake(String flavor,int size){
System.out.println(size+"kg "+flavor);
}
}
Here, bake() works in different ways based on input.
Method Overloading
Example:
Method Overriding
Run-Time Polymorphism
Dynamic binding
When: Decision made by JVM at run time
Rule: Same method name & parameters, but defined in child class
Logic: The behavior depends on the actual object created
Types of Polymorphism
Example:
class Cake{
void bake(){
System.out.println("Baking generic cake");
}
}
class ChocolateCake extends Cake{
@Override
void bake(){
System.out.println("Baking chocolate cake");
}
The correct bake() runs based on the object.
Method Overriding
Rules of Method Overriding
Signature Match: Method name, return type, and parameters must be exactly the same.
Access Level: Cannot be more restrictive than the parent (e.g., protected ➔ public is OK, but not private).
Inheritance Only: Only inherited methods can be overridden.
No Constructors: Constructors cannot be overridden (they are not inherited).
Features
Early Binding
Late Binding
Decided at Compile Time
Decided at Run Time
Method Overloading
Method Overriding
Based on method parameters
Based on actual object type
Faster execution
More flexible
Not allowed
Allowed
Interface
Abstract Class
|
Sets rules for classes |
Share code + enforce rules
Abstract, default, static
Abstract or concrete
Multiple (implements many)
Single (extends one)
Constants only
Any type of variable
Not allowed
Allowed
Interface
Abstract Class
|
Sets rules for classes |
Share code + enforce rules
Abstract, default, static
Abstract or concrete
Multiple (implements many)
Single (extends one)
Constants only
Any type of variable
Not allowed
Allowed
Timing
Mechanism
Basis
Advantage
Constructor
Early binding
Late binding
Real world applications
Debit Card
Deducts directly from bank
Credit Card
Charges credits
UPI / Wallet
Via linked virtual address
Bank Payment System
Single interface, multiple payment modes
Phone Call Button
Same action, different connection type
Calling Mom
Via Cellular Network
Calling Office
Via Office Extension line
WhatsApp Calling
Connects via Internet
public void call(Contact c)
public void pay(double amount)
public void pay(double amount)
public void pay(double amount)
Summary
5
Object type decides method call
4
Compile-time and runtime polymorphism types
3
Method overriding changes child behavior
2
Method overloading uses different parameters
1
Polymorphism means many forms
Quiz
Which concept allows the same method to behave differently?
A. Inheritance
B. Encapsulation
C. Polymorphism
D. Abstraction
Which concept allows the same method to behave differently?
A. Inheritance
B. Encapsulation
C. Polymorphism
D. Abstraction
Quiz-Answer
Java - Polymorphism
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