Java 9 features

Java 9, released in September 2017, was a landmark version built around the Java Platform Module System (JPMS, Project Jigsaw), which finally gave the language real encapsulation and explicit dependencies beyond the flat classpath. It also introduced JShell, the interactive REPL for quickly trying out code. On top of that came handy API additions like the collection factory methods (List.of, Set.of, Map.of), private methods in interfaces, and Stream improvements such as takeWhile and dropWhile. Supporting tools like jlink and jdeps arrived too, making it possible to build slim custom runtimes and analyse dependencies. Though most teams now run newer LTS releases, the modular foundation laid in Java 9 carries straight into every modern Java version.