Advanced Java OOP | Inheritance, super Keyword, Method Overriding & Runtime Polymorphism Explained

🎯 Hook Inheritance lets you build powerful class hierarchies — but without understanding super, method overriding, and runtime polymorphism, you'll write brittle code you can't maintain. This video covers every dimension of Java inheritance and shows you exactly how the JVM resolves method calls at runtime. 📌 Topics Covered • Inheritance — what it is, why it exists, and the IS-A relationship • Single, Multilevel, and Hierarchical inheritance in Java • Why Java does NOT support multiple inheritance with classes (diamond problem) • super keyword — accessing parent class fields and methods • super() — calling the parent constructor; placement rules • Constructor chaining in inheritance — implicit vs explicit super() • Method Overriding — same signature in child class redefines parent behavior • @Override annotation — purpose and why you should always use it • Rules of method overriding — return type covariance, access modifier widening • Runtime Polymorphism — parent reference pointing to child object • How the JVM resolves method calls at runtime (vtable dispatch) • Compile-time Polymorphism (overloading) vs Runtime Polymorphism (overriding) • final with inheritance — final class, final method, final variable 🗒️ What Makes This Video Different Runtime method dispatch is visualized with a reference-type vs object-type diagram showing exactly which method gets called and why. ⏱️ Timestamps • 0:00 Introduction • 0:45 Inheritance — IS-A Relationship • 8:20 Types of Inheritance in Java • 16:00 Why No Multiple Inheritance? (Diamond Problem) • 22:30 super Keyword — Fields & Methods • 29:40 super() — Constructor Chaining • 37:00 Method Overriding — Rules & @Override • 47:30 Access Modifier & Return Type Rules • 53:40 Runtime Polymorphism Explained • 1:03:00 JVM Method Dispatch (vtable) • 1:10:00 Compile-Time vs Runtime Polymorphism • 1:16:00 final in Inheritance • 1:20:00 Summary & Interview Questions 👥 Who Is This Video For? • Java learners ready to move beyond basic OOP • Students preparing for OOP-based university exams • Developers preparing for Java technical interviews • Anyone who wants to write clean, extensible class hierarchies 🏷️ Hashtags #Java #OOP #Inheritance #Polymorphism #MethodOverriding #SuperKeyword #RuntimePolymorphism #JavaOOP #JavaInterview #LearnJava