🔥 Polymorphism in Java – The Superpower of OOP!

Imagine a single word with many meanings — like “run”.
🏃 You can run in a park.
💻 A program can run on a computer.
⚡ Electricity can run through wires.

That’s exactly what Polymorphism means in Java — one action, multiple forms!

🎯 What is Polymorphism?

👉 The word Polymorphism comes from Greek: “poly” = many, “morph” = forms.
👉 In Java, polymorphism allows an object to behave differently based on context.
👉 It makes code flexible, reusable, and easier to maintain.

⚡ Types of Polymorphism in Java

1️⃣ Compile-time Polymorphism (Method Overloading)

• Achieved by defining multiple methods with the same name but different parameters.

• Decided at compile-time.

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

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

public class Main {
    public static void main(String[] args) {
        Calculator c = new Calculator();
        System.out.println(c.add(5, 10));      // Calls int method
        System.out.println(c.add(5.5, 10.5));  // Calls double method
    }
}

Output:

15
16.0

👉 Same method name add() but different forms.

2️⃣ Runtime Polymorphism (Method Overriding)

• Achieved when a subclass provides its own implementation of a method already defined in the parent class.

• Decided at runtime using dynamic method dispatch.

class Animal {
    void sound() {
        System.out.println("Animal makes a 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 Main {
    public static void main(String[] args) {
        Animal a;

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

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

Output:

Dog barks
Cat meows

👉 Same method sound() but different behaviors depending on the object.

More Examples:

⚡ 1. Method Overloading (Compile-time Polymorphism)

👉 Same method name, but different parameters (number or type).

class Calculator {
    // Method with 2 integer parameters
    int add(int a, int b) {
        return a + b;
    }

    // Method with 3 integer parameters
    int add(int a, int b, int c) {
        return a + b + c;
    }

    // Method with 2 double parameters
    double add(double a, double b) {
        return a + b;
    }
}

public class Main {
    public static void main(String[] args) {
        Calculator calc = new Calculator();
        
        System.out.println(calc.add(10, 20));        // Calls int add(int,int)
        System.out.println(calc.add(10, 20, 30));    // Calls int add(int,int,int)
        System.out.println(calc.add(5.5, 4.5));      // Calls double add(double,double)
    }
}

Output:

30
60
10.0

👉 Here, the method add() has multiple forms, decided at compile-time.

⚡ 2. Method Overriding (Runtime Polymorphism)

👉 Subclass provides a new implementation of a method already defined in the parent class.

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();  // Calls Dog's sound()

        a = new Cat();
        a.sound();  // Calls Cat's sound()
    }
}

Output:

Dog barks
Cat meows

👉 Here, the method sound() is overridden and resolved at runtime.

✨ Quick Difference:

• Overloading → Same method name, different parameter list.

• Overriding → Same method name & parameters, but different implementation in subclass.

Would you like me to also prepare a side-by-side code infographic (Overloading vs Overriding) for your website?

💡 Real-World Example of Polymorphism

Think of a remote control 🎛️

• The same button power() can turn TV ON/OFF, AC ON/OFF, or Music System ON/OFF depending on the device.

• That’s polymorphism in action!

⚡ Why Use Polymorphism?

✅ Improves code reusability
✅ Increases flexibility
✅ Makes maintenance easier
✅ Supports dynamic behavior

🎯 Quick Recap:

• Method Overloading (Compile-time) → Same name, different parameters.

• Method Overriding (Runtime) → Same method, different implementations.

🔑 Difference Between Method Overloading and Method Overriding in Java