How does the Java Platform Module System (JPMS, introduced in Java 9) change class loading and encapsulation compared to the traditional classpath model?

Prior to JPMS, all classes on the classpath were effectively globally visible to each other regardless of intended internal package boundaries (a public class in any JAR could be accessed by any other code on the classpath); JPMS introduces explicit module boundaries (declared via module-info.java) where a module must explicitly `exports` a package to make it accessible outside the module, and other modules must explicitly `requires` it to use it -- this provides genuine, JVM-enforced strong encapsulation (not just a documentation convention), preventing reflective access to non-exported internals unless the module explicitly `opens` that package, a significant shift from the classpath model's effectively-everything-is-public default.

// module-info.java
module com.example.myapp {
    requires java.sql;
    exports com.example.myapp.api;      // publicly usable by other modules
    // com.example.myapp.internal is NOT exported -- inaccessible outside this module
}