GitHub - AkashKobal/mastering-java: This repository is designed to take you from Java fundamentals to production-grade enterprise systems, while also preparing you for coding rounds, system design interviews, and real-world backend roles.

☕🚀 ULTIMATE JAVA ENGINEERING ROADMAP (ZERO GAPS)

A complete, end-to-end Java engineering repository covering Core Java, Advanced Java, DSA using Java, Spring Framework, Spring Boot, Spring Security, Spring AOP, Spring AI (LLM & RAG), Redis, Kafka, Microservices, Docker, Kubernetes, CI/CD, Cloud Deployment, and Full-Stack Development (React + Spring Boot).

This repository is designed to take you from Java fundamentals to production-grade enterprise systems, while also preparing you for coding rounds, system design interviews, and real-world backend & full-stack roles.

📌 Who This Repository Is For

Aspiring Java / Backend / Full-Stack Developers
Engineers preparing for coding rounds & interviews
Developers upgrading to modern Spring Boot, Microservices, Cloud & AI
Anyone who wants a single, structured Java roadmap without gaps
Below is the final, corrected, and fully exhaustive Java + Spring Boot industry roadmap.
This is a true end-to-end Java Backend / Full-Stack Engineering roadmap.

🧭 Learning Roadmap

PHASE 0: Prerequisites (Mandatory Foundations)

PHASE 1: Java Fundamentals (Core Java)

PHASE 2: Methods, Memory & Language Internals

PHASE 3: Object-Oriented Programming (CRITICAL)

PHASE 4: Strings, Arrays & Core APIs

PHASE 5: Exception Handling & IO

PHASE 6: Collections Framework (TOP PRIORITY)

PHASE 7: Generics & Advanced Core Java

PHASE 8: Multithreading & Concurrency

PHASE 9: Java 8 → Modern Java (Advanced Language Features)

PHASE 10: Build Tools, IDE & Testing

PHASE 11: JDBC & Hibernate / JPA

PHASE 12: Web Development (Legacy + Foundation)

PHASE 13: Spring Framework (CORE)

PHASE 14: Spring AOP

PHASE 15: Spring Boot (MANDATORY)

PHASE 16: Data Access with Spring Boot

PHASE 17: Spring Security

PHASE 18: JWT & OAuth2

PHASE 19: Redis & Kafka

PHASE 20: Microservices Architecture

PHASE 21: Cloud Deployment

PHASE 22: Docker & Kubernetes

PHASE 23: CI/CD & DevOps

PHASE 24: Frontend (Full-Stack Support)

PHASE 25: Spring AI (Generative AI)

PHASE 26: Data Structures & Algorithms (INTERVIEW)

PHASE 27: System Design & Interview Prep

PHASE 0: Prerequisites (Mandatory Foundations)

Basics of Computer Programming
Basic SQL
Command Line and Git Basics

PHASE 1: Java Fundamentals (Core Java)

Java Basics

Java overview & history
JVM, JRE, JDK
Java versions (8 → 21 LTS)
Environment setup (IntelliJ, Eclipse, STS)
Hello World (plain Java + Maven)
Keywords & identifiers
Variables & constants
Primitive & non-primitive data types
Type Conversion and Type Casting (implicit & explicit)
Java literals
Naming conventions
Code blocks, indentation & statements

Operators & Decision Making

Arithmetic operators
Relational operators
Logical operators
Assignment operators
Ternary operator
if / else / else-if
switch case

Loops & Flow Control

for loop
while loop
do-while loop
enhanced for loop
nested loops
break & continue
loop selection best practices

PHASE 2: Methods, Memory & Language Internals

Method declaration & invocation
Return types
Method overloading
Call by value vs call by reference
Stack vs Heap memory
JVM memory areas
Garbage Collection basics

PHASE 3: Object-Oriented Programming (CRITICAL)

Core OOP

Classes & objects
Constructors (default & parameterized)
this keyword
Encapsulation (getters & setters)
Inheritance (single, multilevel)
Method overriding
Polymorphism
Dynamic method dispatch
Composition vs inheritance

Advanced OOP

Access modifiers
final keyword (variable, method, class)
Object class (equals, hashCode, toString)
Upcasting & downcasting
Wrapper classes

PHASE 4: Strings, Arrays & Core APIs

Strings

String immutability
String literals vs String objects
StringBuilder
StringBuffer
String formatting (printf)

Arrays

One-dimensional arrays
Multi-dimensional arrays
Jagged arrays
Array of objects
Enhanced for loop
Limitations of arrays

PHASE 5: Exception Handling & IO

Exception Handling

Exception hierarchy
Checked vs unchecked exceptions
try / catch / finally
Multiple catch blocks
try-with-resources
throw vs throws
Custom exceptions
Global exception handling concepts

Java IO & NIO

File & directory handling
BufferedReader vs Scanner
Serialization & deserialization
Java IO streams
Java NIO overview

PHASE 6: Collections Framework (TOP PRIORITY)

Collection hierarchy
List
- ArrayList
- LinkedList
- Vector
- Stack
Set
- HashSet
- TreeSet
Map
- HashMap
- TreeMap
Queue & Deque
Iterators
Sorting & reversing
Comparable vs Comparator
equals & hashCode contract
Searching under collections
Concurrent collections

PHASE 7: Generics & Advanced Core Java

Generic classes
Generic methods
Bounded type parameters
Wildcards (? extends, ? super)
Type safety

PHASE 8: Multithreading & Concurrency

Thread lifecycle
Thread vs Runnable
Callable
Thread priority & sleep
Race conditions
Synchronization
Synchronized methods & blocks
Static synchronization
volatile keyword
wait(), notify(), notifyAll()
join()
Deadlock & detection
Deadlock prevention (tryLock)
Executor framework
Thread pools
BlockingQueue
CountDownLatch
ReentrantLock

PHASE 9: Java 8 → Modern Java (Advanced Language Features)

Lambda expressions
Functional interfaces
Stream API
forEach
map / filter / reduce / sorted
Parallel streams
Optional
Method references
Constructor references
Date & Time API (java.time)
Records
Sealed classes
Reflection API
Annotations

PHASE 10: Build Tools, IDE & Testing

Maven / Gradle

pom.xml
Dependencies
Build lifecycle
Plugins
Jar plugin
Multi-module projects

Testing

JUnit 5
Mockito
Unit testing
Integration testing
MockMVC
ZeroCode testing

IDE & Debugging

IntelliJ shortcuts
Eclipse debugging
Terminal usage

PHASE 11: JDBC & Hibernate / JPA

JDBC

JDBC architecture
Driver types
CRUD operations
PreparedStatement
Transactions
Connection pooling

Hibernate / JPA

ORM fundamentals
Hibernate architecture
Entity mapping
Relationships
Fetch strategies
JPQL / HQL
Pagination & auditing
MySQL, PostgreSQL integration
H2 for testing

PHASE 12: Web Development (Legacy + Foundation)

JSP, Servlets & JSTL

Servlet lifecycle
JSP basics
Java Beans
JSTL core tags
JSTL functions
JSTL formatting tags
Custom tags
MVC pattern
Forms & validation
Session management
File & image upload
Database integration
CRUD operations
Full JSP-Servlet projects

PHASE 13: Spring Framework (CORE)

Spring vs Spring Boot
Spring Core
IoC & DI
BeanFactory vs ApplicationContext
Spring Bean lifecycle
Bean scopes (singleton, prototype, custom)
Spring Beans
Autowiring
Java-based configuration
DispatcherServlet
Spring MVC
Validation
Logging

PHASE 14: Spring AOP

AOP principles
AOP vs OOP
AOP vs AspectJ
Cross-cutting concerns
@Aspect
Advices
- Before
- After
- Around
- After Returning
- After Throwing
Use cases (logging, security, transactions)

PHASE 15: Spring Boot (MANDATORY)

Spring Boot Basics

Spring Boot architecture
Auto-configuration
Annotations
Starter dependencies
Embedded server
Profiles
Application.properties & YAML
DevTools
Logging
Actuator

Spring Boot REST APIs

REST principles
@RestController
Request mappings
PathVariable & RequestParam
RequestBody
JSON serialization/deserialization
Validation
Exception handling

PHASE 16: Data Access with Spring Boot

Spring Data JPA
CrudRepository vs JpaRepository
Custom queries
Pagination & sorting
Auditing
DTO mapping
ModelMapper

PHASE 17: Spring Security

Authentication vs Authorization
Password encoding (BCrypt)
Role-based access control (RBAC)
Method-level security
Session management
Secure REST APIs
Custom error handling

PHASE 18: JWT & OAuth2

JWT token lifecycle
Refresh tokens
Stateless authentication
OAuth2 (Google Login)
Custom authentication filters

PHASE 19: Redis & Kafka

Redis

Redis architecture
Spring Cache abstraction
Cache strategies
Pub/Sub messaging
Performance optimization

Kafka

Kafka architecture
Topics, partitions & brokers
Producers & consumers
Kafka with Spring Boot
JSON & String messaging
Dynamic listeners
Kafka + ElasticSearch + Grafana

PHASE 20: Microservices Architecture

Monolith vs microservices
Service decomposition
Inter-service communication
RestTemplate
WebClient
OpenFeign
Eureka service registry
API Gateway
Spring Cloud Config Server
Spring Cloud Bus
Sleuth & Zipkin
Resilience4J
Centralized logging (ELK)

PHASE 21: Cloud Deployment

Deploy Spring Boot apps
AWS Elastic Beanstalk
GCP / Azure basics
Environment configs
Production deployment strategies

PHASE 22: Docker & Kubernetes

Docker

Docker fundamentals
Dockerfile
Multi-stage builds
Docker Compose
Containerizing Spring Boot
Containerizing microservices

Kubernetes

Kubernetes architecture
Pods, Services, Deployments
ConfigMaps & Secrets
Load balancing
Auto-scaling
Deploying microservices to K8s

PHASE 23: CI/CD & DevOps

Maven lifecycle
Spring profiles
Git workflows
GitHub Actions
AWS CodePipeline
AWS CodeDeploy

PHASE 24: Frontend (Full-Stack Support)

JavaScript

Basics
Decision making
Loops
Functions
DOM
Async JavaScript

React

React setup
Components
Hooks
Axios
JWT handling
Material UI
CRUD UI with Spring Boot

PHASE 25: Spring AI (Generative AI)

Spring AI fundamentals
LLM integration
Prompt engineering
RAG (Retrieval Augmented Generation)
Vector databases
AI-powered APIs
MCP server integration

PHASE 26: Data Structures & Algorithms (INTERVIEW)

Time & space complexity
Arrays & strings
Recursion & backtracking
Linked lists
Stack & queue
Hashing
Trees & BST
Heap & priority queue
Graphs (BFS, DFS)
Greedy algorithms
Dynamic programming
Sliding window
Two pointers

PHASE 27: System Design & Interview Prep

REST API design
Scalability
Caching strategies
Load balancing
Database indexing
Fault tolerance
High availability
JVM tuning & GC
Design patterns
- Singleton
- Factory
- Builder
- Strategy
Clean code
Mock interviews

This is a complete Java ecosystem roadmap — equivalent to 2–3 years of industry exposure if mastered fully.

Interview Preparation

Core Java Questions
Spring & Spring Boot Q&A
DSA Coding Patterns
System Design Scenarios
Mock Interview Practice

🏆 Highlights

Zero-to-expert Java roadmap
Enterprise-grade backend stack
Cloud-native & microservices ready
AI-powered backend development
Interview & production focused

📌 How to Use This Repository

Follow modules in order
Read README in each folder
Practice DSA alongside Java
Build projects after every phase
Revise interview sections regularly

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