Java Platform Module System (JPMS)
The Java Platform Module System (JPMS), introduced in Java 9, is a feature that organizes Java code into modules to improve application structure, security, and maintainability. It defines modules with explicit dependencies and encapsulated packages, enabling better control over code visibility and reducing classpath issues. This system is part of Project Jigsaw, which aimed to modularize the Java SE Platform itself.
Developers should learn JPMS when building large-scale Java applications that require strong encapsulation, reduced coupling, and improved performance through optimized class loading. It is essential for creating maintainable, scalable systems, especially in enterprise environments or when developing libraries and frameworks that need to manage dependencies cleanly. Use cases include modularizing legacy applications, building microservices, and ensuring secure deployment by restricting access to internal APIs.