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Java Mastery

Object-Oriented. Powerful. Everywhere.

Learn Java from the ground up: variables, control flow, OOP, collections, generics, streams, concurrency, design patterns, reflection, NIO, the Java Memory Model, and modern Java 21 features. A complete curriculum with 95 structured topics across three levels.

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95+

Topics

475+

Exercises

380+

Quiz Questions

Free

Forever

Learning Paths

🌱

Beginner

Complete Java fundamentals: syntax, data types, operators, control flow, loops, arrays, strings, methods, OOP (classes, constructors, encapsulation, inheritance, abstract classes, interfaces), and exception handling.

0/40 done

⚡

Intermediate

Collections Framework (ArrayList, HashMap, TreeMap), Generics, functional programming (lambdas, streams, Optional), advanced OOP (enums, nested classes, Comparable), exception handling, File I/O (NIO), concurrency basics (threads, ExecutorService), and modern Java features (var, records, text blocks, sealed classes, pattern matching).

0/35 done

🚀

Advanced

Advanced concurrency (CompletableFuture, ReentrantLock, atomic variables, concurrent collections, ForkJoin), design patterns (creational, structural, behavioral, SOLID), reflection and annotations, dynamic proxies, type erasure, advanced streams, NIO buffers and channels, Java Memory Model, pattern matching for switch, virtual threads, and structured concurrency.

0/20 done

Latest Topics

🌱Beginner

What is Java?

Learn what Java is, why it matters, and the key ideas that make it one of the most used programming languages in the world.

15 min

🌱Beginner

Setting Up Java

Install the JDK, choose an IDE, and get your development environment ready to write and run Java programs.

15 min

🌱Beginner

Hello World - Your First Program

Write and understand your first Java program: the anatomy of a class, the main method, and printing output.

15 min

🌱Beginner

How Java Works (JVM, JRE, JDK)

Understand the journey from Java source code to running program: the compiler, bytecode, and the Java Virtual Machine.

15 min

🌱Beginner

Comments in Java

Learn the three types of Java comments and when to use each one to make your code more readable.

10 min

🌱Beginner

Variables

Learn how to declare, initialise, and name variables in Java - the containers that store data in your programs.

15 min

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What's Covered

✓40 beginner topics: variables, operators, control flow, loops, arrays, strings, methods, and OOP

✓35 intermediate topics: Collections, Generics, Streams, File I/O, Concurrency, and Modern Java

✓20 advanced topics: CompletableFuture, design patterns, reflection, NIO, JMM, virtual threads, and Java 21 features

✓Run Java code directly in the browser with instant output

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