Java Overview & Environment Setup (JDK 21)
What Java is, why it dominates backend development, how the JVM works, and a step-by-step JDK installation with your first Hello World program.
Java Tutorial
The most widely used backend language: JVM ecosystem, strong typing, enterprise-grade frameworks.
All 6 tutorials
Java Syntax Basics: Variables, Types, Control Flow & Methods
Primitive and reference types, var keyword, operators, if/switch/for/while, arrays and method definitions — the complete syntax foundation for writing Java.
Object-Oriented Programming in Java: Classes, Inheritance & Interfaces
Classes and objects, encapsulation with access modifiers, inheritance and polymorphism, abstract classes vs interfaces, and the modern record type — core OOP for backend Java.
Java Collections Framework: List, Set, Map & Generics
ArrayList vs LinkedList, HashSet and TreeSet, HashMap internals, iteration, Comparable and Comparator, and how generics keep collections type-safe.
Java Concurrency: Threads, Locks, Thread Pools & CompletableFuture
Creating threads, synchronized and volatile, ReentrantLock, ThreadPoolExecutor parameters, and composing async work with CompletableFuture — the concurrency knowledge backend interviews demand.
Spring Boot for Beginners (2026 Edition)
Build a Spring Boot 3 application from zero: starter dependencies, auto-configuration, application.yml, RESTful APIs, validation, unit testing and jar packaging with full source code.