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What is Polymorphism?

Polymorphism means "many forms" — the ability of an object to take many forms.
In Java, it allows the same method name to perform different tasks, depending on:

• The type of parameters
• The object calling the method

Types of Polymorphism

Type	Description	Example
Compile-time Polymorphism	Method Overloading	Same method name, different parameters
Runtime Polymorphism	Method Overriding	Same method name, same parameters, different class

Method Overloading (Compile-Time)

Same method name, but different number/type/order of parameters in same class.

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;
        }
    }

    public class Main {
        public static void main(String[] args) {
            Calculator c = new Calculator();
            System.out.println(c.add(2, 3));         // int version
            System.out.println(c.add(2.5, 3.5));     // double version
            System.out.println(c.add(1, 2, 3));      // 3 parameters
        }
    }
    
    

Output:

    
    5
    6.0
    6
    
    

Overloading helps in code clarity and flexibility.

Method Overriding (Runtime)

Child class redefines a method of the parent class with same name and parameters.

Example:

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

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

    public class Main {
        public static void main(String[] args) {
            Animal a = new Dog();  // Polymorphism in action
            a.sound();             // Calls Dog's sound()
        }
    }
    
    

Output:

    
    Dog barks
    
    

The method that runs is decided at runtime, depending on the object type.

Key Differences

Feature	Overloading	Overriding
Occurs in	Same class	Parent-child class
Parameters	Must differ	Must be same
Return type	Can differ	Should be same or covariant
@Override used?	No	Yes
Resolved at	Compile-time	Runtime

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