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Intermediate 18 min readModule: Module 5: Inheritance, Polymorphism & Abstract Classes

Inheritance, Dynamic Polymorphism & @Override

Extend parent classes, override methods dynamically, and define abstract templates.

What You Will Learn in This Lesson

  • Extending classes with the 'extends' keyword
  • Runtime dynamic method dispatch (polymorphism)
  • Abstract classes that cannot be directly instantiated

Introduction & Core Concept

Inheritance allows child classes to inherit attributes and methods from a parent class, promoting code reuse. Polymorphism allows subclasses to provide customized method implementations.
WHY DOES THIS MATTER IN THE REAL WORLD?

Polymorphism lets you write code that operates on a generic PaymentMethod base class without caring whether it is CreditCard or PayPal.

Polymorphic Payment Processing

java
java
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public abstract class PaymentMethod {
    public abstract void processPayment(double amount);
}
 
public class CreditCardPayment extends PaymentMethod {
    @Override
    public void processPayment(double amount) {
        System.out.println("Processing credit card charge: $" + amount);
    }
}

Line-by-Line Technical Breakdown

1Java supports single inheritance for classes (a class can only extend one parent class).

Try It Yourself (Interactive Editor)

Modify the code in real-time and click Run to test live browser output and console logs.

Intelligent Code Runner & Live Sandbox[JAVA]
JAVA SOURCE EDITOR
Interactive Live Code

Industry Best Practices & Professional Standards

  • Prefer composition over inheritance for sharing code between unrelated classes.

Lesson Summary & Core Takeaways

  • Polymorphism enables flexible, extensible object-oriented architectures.