Java
Learn Java from your very first compiled program to real, tested command-line applications. A practice-first path: write Java from lesson one, read real compiler errors and stack traces, and build a foundation of object-oriented design, collections, and modern Java idioms that scales to professional codebases.
Java — Beginner
Start programming with Java: the compile-run model, types and control flow, methods, classes and objects, collections, generics, exceptions, files, streams, tests, and Maven — writing real Java from the first lesson to a full capstone application.
Java — Intermediate
Move from writing Java to engineering it: equality and immutability contracts, SOLID design, generics with wildcards, advanced collections, Collectors, exception architecture, testing depth, concurrency, async composition, repositories, layered architecture, and algorithms — capped by a layered expense-tracker capstone.
Java — Advanced
Understand Java deeply enough to optimize, secure, and operate it: the object and memory model, bytecode, reflection-driven design, the Java Memory Model, lock-free concurrency, virtual threads, GC and performance method, high-performance I/O, real loopback networking, persistence and distribution concepts, security, observability, and a production-grade capstone.