Udemy – Java Coding Practice: 90+ Exercises, OOP to Concurrency

Most “Java practice” courses give you a handful of toy problems and call it a day. This one gives you 90 real, working coding exercises — every single one compiled and executed before it was published, not just written and hoped for.

You’ll build fluency through deliberate practice across three progressive tiers:

• BEGINNER (20 exercises): Methods, control flow, strings, arrays, collections, basic OOP (classes, constructors, inheritance, method overloading), exceptions, and HashMaps — the fundamentals, done properly.
• INTERMEDIATE (25 exercises): Generics, interfaces and abstract classes, custom exceptions, lambdas and the Stream API, Optional, TreeMap and PriorityQueue, regex, enums, recursion, custom Iterable implementations, reading/writing via stdin and stdout, and verifying encapsulation through reflection.
• ADVANCED (30 exercises): Modern Java 21 features (records, sealed interfaces, pattern-matching switch, text blocks), advanced Stream collectors, six classic design patterns (Singleton, Factory, Strategy, Observer, Decorator, Adapter), concurrency fundamentals (threads, synchronized, AtomicInteger, ExecutorService, CountDownLatch, ConcurrentHashMap), bounded generics, and a 4-part capstone building a thread-safe, filterable event bus from scratch.