How does the introduction of the module system in Java 9 impact application architecture?

The Java Module System, introduced in Java 9 through Project Jigsaw, encourages a more modular application architecture by dividing large applications into smaller, well-defined modules. Each module explicitly declares its dependencies and controls which packages are exposed, resulting in better maintainability, security, and scalability.

Key Points: • Modules define explicit dependencies using the requires keyword, making application architecture more transparent and easier to manage. • Strong encapsulation hides internal implementation details and exposes only selected APIs through the exports keyword. • Modular applications are easier to maintain, test, deploy, and optimize because only required modules need to be loaded.

Example: In a banking application, separate modules can be created for customer management, payments, loans, and reporting. Each module exposes only its public APIs while keeping internal classes inaccessible to other modules.

Code Example:

module com.banking.payment {

    requires com.banking.customer;

    exports com.banking.payment.api;
}

module com.banking.customer {

    exports com.banking.customer.api;
}

Interview Tip: A concise interview answer is: The Java 9 Module System improves application architecture by introducing explicit dependency management and strong encapsulation. It enables applications to be organized into independent modules, making them more maintainable, secure, scalable, and easier to deploy than traditional monolithic applications.