Java · Spring · Cloud

Master Java Backend Engineering

A structured, interview-ready knowledge base for Java backend engineers. Built from first principles — core Java to cloud-native Spring Boot.

UserController.java

1@RestController

2@RequestMapping("/api")

3public class UserController {

5 @Autowired

6 private UserService userService;

8 @GetMapping("/users")

9 public List<User> getAll() {

10 // returns all users

11 return userService.findAll();

12 }

13}

34Domains Covered

Java 8 → 21Version Coverage

100+Interview Questions

FreeAlways & Forever

What's Inside

34 domains covering the full Java backend engineering stack

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Designed to build deep, durable understanding — not just pass interviews

🧱

Every topic starts with why before how. Understand the problem that motivated a solution before learning to use it.

📈

Each note builds from basics to advanced on the same page — no hunting across separate beginner and advanced docs.

🎯

Every domain includes Q&A at Beginner → Intermediate → Advanced, calibrated for real backend engineering interviews.

🔗

Notes cross-link meaningfully. Follow the thread from Spring beans → IoC → DI → testing without losing context.