A deep-dive reference guide into the Java ecosystem, covering everything from JVM internals and concurrency to Spring, Hibernate, and beyond. Built for Java developers who want to go beyond syntax and ace technical interviews.
| File | Description |
|---|---|
| Core-Java.md | 150 core Java concepts covering OOP, generics, functional programming, streams, modern Java features, and more |
| JVM.md | 53 JVM concepts covering memory areas, garbage collection, class loading, bytecode, JIT compilation, and runtime optimizations |
| Concurrency.md | 64 concurrency concepts covering threads, locks, memory model, async programming, virtual threads, and parallel streams |
| Collections.md | 200 collections concepts from basics to specialized collections including iterator internals, concurrent collections, queue & heap structures, performance & memory |
| Design-Patterns.md | 150 design pattern concepts from fundamentals to enterprise architecture including SOLID principles, creational patterns, structural patterns, behavioral patterns, design smells, refactoring, CQRS, Saga, Repository, DAO, MVC, Hexagonal Architecture, Ports & Adapters, and pattern selection strategies |
| Spring-Framework.md | 150 Spring Framework concepts from foundations to advanced container internals including IoC, Dependency Injection, Bean Lifecycle, Bean Scopes, AOP, Transaction Management, Three-Level Cache, Circular Dependency Resolution, Proxy Mechanisms, Context Internals, Performance Optimization |
| Spring-Boot.md | 150 Spring Boot concepts covering fundamentals, auto-configuration, starters, configuration management, Actuator, REST APIs, WebFlux, observability, metrics, Docker, Kubernetes, native images, and production best practices |
| Spring-Data-JPA.md | 162 Spring Data JPA concepts covering JPA fundamentals, entity mapping, repositories, JPQL, Criteria API, Hibernate internals, caching, transactions, locking, performance optimization, auditing, database migrations, and JPA architectural best practices |
Each concept is documented with the following structure:
- Actual Meaning — what the concept truly is, beyond surface-level definitions
- Why It Exists — the problem it was designed to solve
- Common Misconception — myths and misunderstandings clarified
- Real Purpose — the deeper intent behind the design
- Real World Example — practical scenarios from Spring Boot and enterprise Java
- Interview Depth — questions and angles explored in technical interviews
- Related Topics — connected concepts to build a complete mental model
- Java developers preparing for technical interviews
- Engineers who want to understand what happens beneath the Java code
- Anyone building high-performance, production-grade Java applications
