This repository is a structured, in-progress learning journal for mastering Java from core fundamentals to AI-powered backend engineering. It is being built incrementally, topic by topic, while learning and practicing.
The goal of this repository is to:
- Build strong Java and Spring Boot foundations
- Practice concepts with clear, minimal examples
- Cover the full backend engineering stack — from OOP to RAG pipelines
- Serve as a revision and interview-prep reference
This is not a finished project. Files are added gradually as concepts are learned and understood.
🚧 Work in Progress New files and examples are added continuously while learning and practicing.
01_Java_Basics
02_OOP
03_Core_APIs
04_Collections_And_Algorithms
05_Exceptions_And_Logging
06_File_And_IO
07_Concurrency_And_Threads
08_Java_Memory_And_JVM
09_Design_Patterns
10_Spring_Basics
11_Databases_And_JPA
12_Spring_REST_And_Security
13_Testing
14_Tools_And_Build
15_Interview_Questions
16_Java_Patterns
17_Spring_AI
18_LangChain4j_And_RAG
Each folder focuses on one major concept, with:
- Small, focused examples
- Clear class and method names
- Practical scenarios instead of theory-only code
- Data types and operators
- Control flow (if, switch, loops)
- Methods and basic programs
- Classes and objects
- Encapsulation, Inheritance, Polymorphism
- Abstraction and Interfaces
- Generics — type-safe templates, bounded types, wildcards
- Lambdas — functional interfaces, method references
- Stream API — filter, map, reduce, collectors
String,Math,Objects, Wrapper classes- Utility classes
- List, Set, Map, Queue and Deque implementations
- Iteration techniques
- Searching and sorting
- Checked vs unchecked exceptions
- Custom exceptions
- Try-catch-finally
- Basic logging concepts
- File handling
- Byte and character streams
- Buffered IO
- Thread creation and lifecycle
- Synchronization and deadlocks
ExecutorServiceand thread poolsCompletableFutureand async tasks- Producer-consumer pattern
- Heap vs Stack
- Garbage Collection
- JVM architecture
- Singleton, Factory, Builder
- Observer, Strategy
- Dependency Injection
- Spring annotations and bean lifecycle
- Application context
- JDBC basics
- JPA annotations and ORM concepts
- Entity relationships (
@OneToMany,@ManyToOne) JpaRepositoryand custom queries
@RestControllerand REST API design- Full CRUD API implementation
- Global exception handling with
@ControllerAdvice - Spring Security basics and filter chain
- JWT authentication — register, login, token validation
- JUnit basics
- Mockito
- Integration tests
- Maven and Gradle
- Git workflow and project structure
- Java Core Q&A
- OOP Q&A
- Collections Q&A
- Spring Q&A
- Concurrency Q&A
- Star and number patterns
- Logic and output-based problems
- Setup and configuration (
spring-ai-openai) /chatendpoint with LLM integration- Prompt templates with dynamic variables
- Embedding client
@AiServiceinterface
- LangChain4j basics and
@AiService - Conversation memory (
ChatMemory) - Embeddings and
pgvectorsetup - Document loading and chunking
- Full RAG pipeline —
/askendpoint with vector retrieval
- Files are added only after understanding the concept
- Code is kept simple and readable
- Emphasis on clarity over optimization
- Refactoring happens as learning improves
- Browse folders topic-wise
- Run individual classes directly
- Use it for:
- Revision
- Interview preparation
- Concept clarification
This repository is primarily for personal learning.
However:
- Suggestions
- Documentation improvements
- Code readability improvements
are welcome via Pull Requests.
- This repository reflects learning progress, not perfection
- Some sections may be incomplete or evolving
- Improvements will be continuous
Maintained by Skakarla2023 B.Tech CSE student building toward an AI Backend Engineer role — Java, Spring Boot, Spring AI, LangChain4j.
If you are learning Java backend engineering, feel free to explore, fork, or adapt the structure for your own practice.