Skip to content

26Polymorphism

Directory actions

More options

Directory actions

More options

Latest commit

 

History

History

26Polymorphism

readme.md

☕ Java Lesson – Polymorphism (Compile-Time & Run-Time)

Is lesson me hum seekhenge:

  • Polymorphism kya hota hai
  • Method Overloading
  • Method Overriding
  • Compile-time polymorphism
  • Run-time polymorphism
  • Upcasting ka role polymorphism me
  • Downcasting

1️⃣ Polymorphism Kya Hota Hai?

Polymorphism ka matlab:

Ek hi cheez ka multiple forms me behave karna

Java me:

Ek method alag-alag situations me different behavior dikha sakta hai

Real life example:

Ek aadmi:
Student bhi ho sakta hai
Teacher bhi
Employee bhi

Same person → multiple roles

2️⃣ Java me Polymorphism ke Types

Java me polymorphism 2 tarah ka hota hai:

1. Compile-time Polymorphism
2. Run-time Polymorphism

3️⃣ Compile-Time Polymorphism

Isse kehte hain:

Method Overloading

Yahan method ka decision compile time par hota hai.

4️⃣ Method Overloading

Jab ek hi class me same method name ho lekin:

parameters different ho

Example:

class MathUtils {

    int add(int a, int b){
        return a + b;
    }

    int add(int a, int b, int c){
        return a + b + c;
    }
}

Usage:

public class Test {

    public static void main(String[] args){

        MathUtils m = new MathUtils();

        System.out.println(m.add(2,3));
        System.out.println(m.add(2,3,4));
    }
}

Output

5
9

5️⃣ Run-Time Polymorphism

Isse kehte hain:

Method Overriding

Yahan decision run time par hota hai.

6️⃣ Method Overriding

Jab child class parent class ke method ko same signature ke saath redefine kare.

Example:

class Animal {

    void sound(){
        System.out.println("Animal sound");
    }
}

class Dog extends Animal {

    void sound(){
        System.out.println("Dog barks");
    }
}

7️⃣ Runtime Polymorphism Example

public class Test {

    public static void main(String[] args){

        Animal a = new Dog(); // upcasting

        a.sound(); // run-time decision
    }
}

Output

Dog barks

Yahan:

reference → Animal
object → Dog

Phir bhi Dog ka method call hua.

Isko kehte hain:

Dynamic Method Dispatch

8️⃣ Compile-time vs Run-time Polymorphism

Feature Compile-time Run-time
Concept Overloading Overriding
Decision time Compile time Run time
Inheritance required ❌ No ✔ Yes
Performance Fast Slightly slow

9️⃣ Rules of Method Overriding

✔ Method name same hona chahiye
✔ Parameters same hone chahiye
✔ Return type same ya covariant hona chahiye
✔ Access modifier same ya more public hona chahiye

🔟 Example – Overloading vs Overriding

class Shape {

    void draw(){
        System.out.println("Drawing shape");
    }

    void draw(String color){
        System.out.println("Drawing shape in " + color);
    }
}

class Circle extends Shape {

    @Override
    void draw(){
        System.out.println("Drawing circle");
    }
}

1️⃣1️⃣ Polymorphism + Object Array Example

class Animal {

    void sound(){
        System.out.println("Animal sound");
    }
}

class Dog extends Animal {

    void sound(){
        System.out.println("Dog barks");
    }
}

class Cat extends Animal {

    void sound(){
        System.out.println("Cat meows");
    }
}

public class Test {

    public static void main(String[] args){

        Animal[] animals = {
            new Dog(),
            new Cat()
        };

        for(Animal a : animals){
            a.sound();
        }
    }
}

Output

Dog barks
Cat meows

1️⃣2️⃣ Polymorphism Ka Real Use

Use hota hai:

framework design
collections
dynamic behavior
clean architecture

Example:

List list = new ArrayList();
List list = new LinkedList();

Same reference → different implementation.

🎯 Interview Questions

1️⃣ Polymorphism kya hota hai?
2️⃣ Compile-time aur run-time polymorphism me difference kya hai?
3️⃣ Method overloading aur overriding me difference kya hai?
4️⃣ Dynamic method dispatch kya hota hai?
5️⃣ Upcasting polymorphism me kaise help karta hai?

🧾 Lesson Summary

Is lesson me humne seekha:

✔ Polymorphism concept
✔ Compile-time polymorphism (Overloading)
✔ Run-time polymorphism (Overriding)
✔ Dynamic method dispatch
✔ Real-world usage

Polymorphism Java OOP ka sabse powerful feature hai jo flexible aur extensible code likhne me help karta hai.