1. Introduction to Polymorphism

1.1 What is Polymorphism

Polymorphism means “many forms.” In Java, it allows methods or objects to behave differently based on context.

1.2 Types of Polymorphism

Compile-time polymorphism
Runtime polymorphism

1.3 Importance

Improves code flexibility
Promotes reusability
Simplifies code design

1.4 Real-World Example

A person can have multiple roles:

Teacher
Parent
Employee

2. Method Overloading (Compile-Time Polymorphism)

2.1 Definition

Method overloading occurs when multiple methods have the same name but different parameters.

2.2 Example

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;
    }
}

2.3 Rules

Method name must be same
Parameters must differ (number or type)
Return type alone is not enough

2.4 Advantages

Improves readability
Reuses method name

3. Method Overriding (Runtime Polymorphism)

3.1 Definition

Method overriding occurs when a subclass provides its own implementation of a method defined in the parent class.

3.2 Example

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

3.3 Rules

Same method name
Same parameters
Same return type
Must use inheritance

3.4 Dynamic Method Dispatch

The method to be executed is decided at runtime.

Animal a = new Dog();
a.sound();  // Calls Dog's method

3.5 @Override Annotation

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

3.6 Advantages

Supports runtime flexibility
Enables dynamic behavior

4. Compile-Time vs Runtime Polymorphism

4.1 Compile-Time Polymorphism

Achieved using method overloading
Decision made at compile time

4.2 Runtime Polymorphism

Achieved using method overriding
Decision made at runtime

4.3 Differences

Feature	Compile-Time	Runtime
Method	Overloading	Overriding
Binding	Early binding	Late binding
Decision Time	Compile time	Runtime
Performance	Faster	Slightly slower

4.4 Use Cases

Overloading → Same operation with different inputs
Overriding → Different behavior in subclasses

Conclusion

Polymorphism is a powerful feature in Java that allows flexibility and dynamic behavior in programs. By understanding method overloading and overriding, beginners can write cleaner, more reusable, and scalable code. This concept is widely used in real-world applications and is essential for mastering Object-Oriented Programming.

Polymorphism