What is Polymorphism?

🔄 What Is Polymorphism?

Polymorphism simply means “many forms.” In Java, it lets the same method or object behave in different ways depending on the situation.

💡 Think of it like this:

Imagine a single remote control that can operate a TV, a speaker, or an AC. It’s the same remote, but depending on which device it’s controlling, the function changes. That’s polymorphism in action.

There are two main types:

1. Compile-Time Polymorphism (Static Binding)

Achieved through method overloading—same method name, different parameter lists.

2. Runtime Polymorphism (Dynamic Binding)

Achieved through method overriding—a subclass provides a specific implementation of a method already defined in its superclass.

🧪 1. Compile-Time Polymorphism (Method Overloading)

class Printer {
    void print(String msg) {
        System.out.println("Message: " + msg);
    }
    void print(int number) {
        System.out.println("Number: " + number);
    }
}

// Usage
Printer p = new Printer();
p.print("Hello");  // Message: Hello
p.print(123);      // Number: 123

Usage:

Printer p = new Printer(); p.print(“Hello”); // Message: Hello p.print(123); // Number: 123

The compiler decides which method to call based on the argument type.

🧪 2. Runtime Polymorphism (Method Overriding)

class Animal {
void makeSound() {
System.out.println(“Animal makes a sound”);
}
}

class Dog extends Animal {
@Override
void makeSound() {
System.out.println(“Dog barks”);
}
}

// Usage
Animal a = new Dog();
a.makeSound(); // Output: Dog barks

Usage:

Animal a = new Dog();

a.makeSound(); // Output: Dog barks

Even though the reference is of type Animal, the actual method called is from Dog—decided at runtime.

🧠 Why Use Polymorphism?

• Code Reusability: Write generic code that works with multiple types.
• Flexibility: Add new behaviors without changing existing code.
• Maintainability: Cleaner, more modular code.

🌍 Real-World Examples of Polymorphism

✅ 1. Payment Processing System

interface Payment { void pay(double amount); } class CreditCard implements Payment { public void pay(double amount) { System.out.println(“Paid ₹” + amount + ” using Credit Card”); } } class UPI implements Payment { public void pay(double amount) { System.out.println(“Paid ₹” + amount + ” using UPI”); } }

Usage:

Payment payment = new UPI(); payment.pay(500); // Output: Paid ₹500 using UPI

The same pay() method behaves differently depending on the payment method.

✅ 2. Media Player

A MediaPlayer class might have a method play():

• AudioPlayer plays MP3s
• VideoPlayer plays MP4s
• StreamingPlayer plays online content

All override the same play() method, but the behavior changes based on the media type.

✅ 3. Human Roles

A person can be:

• A teacher in school
• A parent at home
• A customer in a store

Same person, different behaviors depending on the context—just like polymorphism!