Spring

Complete Java Interview Prep Sheet (Final Version) 1. Core OOP Concepts 4 Fundamental Principles: Abstraction: Hide implementation details, show only essential features (abstract classes/interfaces). (what to implement). Encapsulation: Bundle data + methods, hide internals using private fields + public getters/setters (data hiding). Inheritance: Child class acquires parent class properties (is-a relationship, single inheritance only). Polymorphism: Same interface, multiple forms (compile-time: method overloading; runtime: method overriding). Key Points: Java not pure OOP (uses primitives, no multiple class inheritance). Object class is root of all classes: equals(), hashCode(), toString(), wait()/notify(). Multiple inheritance via interfaces only (no diamond problem). 2. Java Basics Class/Object/Method: ...