👋 New to Java? Start here.
Follow this path in order — each step builds on the last.
Your learning path
📑 Reference Pages
Deep dives into each part of Java. Read when you need to understand something properly, or use as a lookup while coding.
Java Overview
JVM, compilation, the Java ecosystem, versions.
Variables & Types
Primitives, reference types, boxing, type system.
OOP
Classes, inheritance, interfaces, abstract classes, polymorphism.
Collections & Generics
List, Map, Set, generics, iterators, Comparable.
Exceptions
Checked vs unchecked, try/catch/finally, custom exceptions.
Streams & Lambdas
Functional interfaces, stream pipeline, filter/map/reduce.
Concurrency
Threads, synchronized, ExecutorService, CompletableFuture.
▶ Run Code & Copy Snippets
Copy ready-to-use code patterns or run Java right in your browser.
🛠 Projects
60 projects available in Python — Java versions are planned. The logic is identical across languages.
🟩 Foundations
Short programs using basic syntax only.
Number Guessing Game
To-Do List
📊 Go Further
Compare Java to Other Languages
Side-by-side syntax comparison across all 11 languages on The Codex.
History of Programming Languages
How Java came to be, what problems it solved, and how it fits the bigger picture.
Programming Glossary
Plain English definitions for 80 terms — variable, function, loop, class, API, and more.