What is Polymorphism?

Polymorphism means "many forms".

In Java, polymorphism allows a single action to behave differently based on the object that performs it.

👉 It enables one interface to be used for different underlying data types.

Types of Polymorphism in Java:

1. Compile-time Polymorphism (Method Overloading)
2. Runtime Polymorphism (Method Overriding)

1. Compile-time Polymorphism (Method Overloading)

Occurs when multiple methods have the same name but different parameters (number or type).

Example: Method Overloading

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

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

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

public class Main {
    public static void main(String[] args) {
        Calculator calc = new Calculator();
        System.out.println(calc.add(2, 3));        // 5
        System.out.println(calc.add(2.5, 3.5));    // 6.0
        System.out.println(calc.add(1, 2, 3));     // 6
    }
}

2. Runtime Polymorphism (Method Overriding)

Occurs when a child class provides a specific implementation of a method that is already defined in the parent class.

Example: Method Overriding

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

class Dog extends Animal {
    @Override
    void sound() {
        System.out.println("Dog barks");
    }
}

class Cat extends Animal {
    @Override
    void sound() {
        System.out.println("Cat meows");
    }
}

public class Main {
    public static void main(String[] args) {
        Animal a;

        a = new Dog();
        a.sound();  // Dog barks

        a = new Cat();
        a.sound();  // Cat meows
    }
}

Real-life Analogy of Polymorphism:

• Method Name: draw()
• Circle.draw() → draws a circle
• Rectangle.draw() → draws a rectangle
• Same method name → different behavior depending on the object type

Key Differences Between Overloading & Overriding:

Summary