What is Polymorphism?

Polymorphism is a big word that simply means “many forms.”
In Java, it means one action can behave differently depending on the object.
Real-Life Example: Remote Control

Imagine you have one remote control that can:
Control a TV
Control an AC
Control a projector

You’re pressing the same button, but it performs different actions based on the device.
That’s polymorphism in real life—same action, different behavior.

In Java: What does it mean?

In Java, polymorphism allows one method or one object to behave in multiple ways.
There are two types:

1. Compile-time Polymorphism (Method Overloading)

2. Runtime Polymorphism (Method Overriding)

1. Compile-time Polymorphism (Method Overloading)
Same method name, but different parameters.
Example: Calculator

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

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

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

add(2, 3) → returns 5
add(2.5, 3.1) → returns 5.6
add(1, 2, 3) → returns 6

Same method name (add), but it works differently depending on inputs.

2. Runtime Polymorphism (Method Overriding)

Same method, but defined differently in child classes.

Example: Animal Sounds

class Animal {
    public void makeSound() {
        System.out.println("Some sound");
    }
}

class Dog extends Animal {
    public void makeSound() {
        System.out.println("Bark");
    }
}

class Cat extends Animal {
    public void makeSound() {
        System.out.println("Meow");
    }
}

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

        a = new Dog();
        a.makeSound(); // Output: Bark

        a = new Cat();
        a.makeSound(); // Output: Meow
    }
}

Even though a is declared as Animal, the method behaves differently depending on the actual object (Dog or Cat).

Why is Polymorphism Useful?
1. Flexibility – Same code works in different ways.
2. Reusability – Code becomes reusable and cleaner.
3. Scalability – Easy to add new behaviors without changing existing code.
4. Maintainability – Easier to fix and manage.

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