Java Interview Notes — Deep & Easy Edition

21 topics of core Java through concurrency and Java 8, each explained with a simple everyday analogy first, then full technical depth, a working code example with output, an interview tip, and common interview Q&A — variables and scope, the four pillars of OOP, abstract class vs interface, key keywords (this/super/static/final), arrays/strings/number systems, exception handling, the Collections Framework, multithreading and concurrency, Java 8+ features, JVM memory management and garbage collection, serialization, design patterns and generics, annotations and reflection, inner classes, immutability, and file handling.