Beginner Intermediate Advanced Basics 26 Strings 17 Collections 30 IO 16 Advanced 30 Modern Java 20 Testing 5 Reactive 4 JVM 5 JDBC 5 Networking 5 Cryptography 5 Concurrency 7 XML 5 JSON 5 Java Basics 26 articles Java Strings 17 articles Java Collections 30 articles List6 Map7 Set, Queue & Deque3 Iterators, Sorting & Utilities6 Java IO 16 articles Advanced 30 articles Modern Java 20 articles Testing 5 articles JVM Performance & Profiling 5 articles Reactive Programming (Project Reactor) 4 articles JDBC — Database Access 5 articles Cryptography 5 articles Networking 5 articles JSON — Jackson Deep Dive 5 articles XML Processing 5 articles Concurrency 7 articles