Learn Java Programming & OOP

Learn Java programming from your first System.out.println to a Spring Boot REST API, one short lesson at a time. Write code in the built-in code editor, run it on a real Java compiler (javac and the JVM, online) and practise with coding exercises after every topic. No IDE or JDK to install. Java is the language behind Android apps, Spring backend services and enterprise systems. This tutorial takes you there step by step, for complete beginners and for developers who want to go deeper into core Java and object-oriented programming.

WHAT YOU'LL LEARN
• The basics: variables, types, casting, operators, strings, if/else, switch and loops
• Methods, arrays, the Scanner class and formatted output with printf
• Object-oriented programming (OOP): classes, objects, inheritance, interfaces, abstract classes, enums and records
• Core collections: List, Set, Map, TreeMap, Deque, iterators and comparators
• Exceptions, files and I/O, the java.time API, Optional and regular expressions
• Generics, lambdas, method references and the Streams API
• Concurrency: threads, ExecutorService, CompletableFuture and virtual threads
• JVM internals: memory, garbage collection, class loading and bytecode
• Backend development: Maven and Gradle, JDBC, Spring Boot, Spring Data JPA, REST APIs and JUnit 5 testing
• 104 courses and 370+ bite-sized lessons, from A1 beginner to C2 advanced level

WRITE AND RUN REAL JAVA CODE
• Every lesson has examples you can edit and run in the code editor
• See compiler errors the way a professional developer sees them, then fix them
• Save your code, take notes and bookmark the lessons you want to review

BUILD REAL PROJECTS
• 20 guided projects, each built step by step
• Every step is checked by compiling and running your code against the expected output
• 60 coding missions with XP for extra coding practice outside the lessons

QUIZZES AND INTERVIEW PREP
• Multiple-choice quizzes (MCQ) with an explanation for every answer
• A Java interview question of the day: JDK vs JRE vs JVM, OOP pillars, String pool, abstract class vs interface and more
• A cheat sheet and a code library for quick review
• Review sessions that bring back what you learned earlier

AI MENTOR
• Stuck on a compiler error, a stream or an OOP concept? Ask the AI Mentor and get a clear explanation
• Select code in the editor and ask the AI to explain, optimize or rewrite it

COMPETE AND GET CERTIFIED
• World Coding Challenge: 3 global coding rounds every day with a live leaderboard
• A daily coding challenge on the home screen
• Certificate exam (Pro): pass it and share your Java certificate
• Streaks, XP, daily reminders and progress tracking keep your practice going

HOW IT WORKS
1. Pick a course and start with a short lesson
2. Run every example in the editor and change it to see what happens
3. Lock it in with a quiz, a project step or a mission
4. Stuck? Ask the AI Mentor, then move on to the next topic

WHO IT'S FOR
• Beginners who want a serious first programming language
• Students who need extra practice for classes and exams
• Developers preparing for Java developer and backend job interviews
• Android and Python developers adding core Java to their skills

FREE TO START
Your first course is free, and you get one AI Mentor question a day. Free users see ads. Pro unlocks every course, all projects and missions and the certificate exam, removes ads and lifts the daily AI Mentor limit.

The app is available in 22 languages. Download Learn Java and write your first program today.

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