Cheat Sheets
One-page quick references for each stage of your journey.
Quick reference sheets
🧩
Core Java Syntax
Variables, types, control flow, and methods at a glance.
Open sheet🚀Collections & Generics
Pick the right data structure and use it correctly.
Open sheet⚡Stream API & Lambdas
Declarative data processing and functional interfaces.
Open sheet🎯Design Patterns
The Gang of Four patterns in one line each.
Open sheet📊Big-O & Data Structures
Complexity classes and structure trade-offs.
Open sheet🌿Spring Annotations
The annotations a Spring developer reaches for every day.
Open sheet🗂️Spring Project Layout
How a typical Spring Boot application is organized (the BookVault shape).
Open sheetStudy index by stage
🏗️
Object-Oriented Programming
1 h 30 min🚀
Intermediate Java
1 h 52 min🔐
Spring Authorization Server
1 h 14 min📊
Advanced Observability
1 h 11 min🎯
Complexity & Problem-Solving
1 h 21 min🔢
Arrays & Strings
1 h 11 min🔗
Linked Lists, Stacks & Queues
1 h 13 min🔍
Heaps, Sorting & Searching
1 h 14 min🧠
Recursion, Backtracking & DP
1 h 19 min💬
The Interview Itself
1 h 8 min🗺️
Domain-Driven Design Lite
1 h 28 min⬡
Hexagonal & Clean Architecture
1 h 28 min🌱
Evolutionary Architecture
1 h 24 min🗺️
Practical System Design
1 h 31 min🟣