7.1.2 Module Path Explained

The module path in Java SE 11 is a crucial concept for managing dependencies and organizing code in a modular system. Understanding the module path is essential for developing modular applications that are scalable, maintainable, and efficient.

Key Concepts

1. Module Path Definition

The module path is a list of directories or JAR files that the Java runtime searches for modules. It is specified using the --module-path or -p option when running Java applications. The module path allows you to include external modules that your application depends on.

Example

        java --module-path mods -m myapp/com.example.Main
    

2. Module Resolution

When you run a Java application with a module path, the Java runtime resolves the modules by searching the directories or JAR files specified in the module path. This process ensures that all required modules are available and can be loaded at runtime.

Example

        java --module-path mods:libs -m myapp/com.example.Main
    

3. Module Dependencies

Modules can have dependencies on other modules. When you specify a module path, you include all the modules that your application depends on. This ensures that all required modules are available and can be used by your application.

Example

        java --module-path mods:libs -m myapp/com.example.Main
    

4. Module Path vs. Classpath

The module path is different from the traditional classpath. The classpath is used to locate classes and resources in non-modular applications, while the module path is used to locate modules in modular applications. Using the module path allows for better organization and encapsulation of code.

Example

        java --module-path mods -m myapp/com.example.Main
    

Examples and Analogies

Think of the module path as a map that guides the Java runtime to find all the necessary modules for your application. Just as a map helps you navigate to different locations, the module path helps the Java runtime navigate to different modules. For example, if your application depends on a module named "database", you would include the directory containing the "database" module in the module path.

By mastering the module path, you can efficiently manage dependencies and organize your code in a modular system, ensuring that your applications are scalable, maintainable, and efficient.