What is a module in Java hierarchy?

Hayden 108 Published: 09/26/2024

What is a module in Java hierarchy?

I'd be happy to explain what a module is in the Java hierarchy.

In the Java programming language, a module is a new concept introduced with Java 9 (JDK 9) as part of Project Jigsaw, which aims to improve the modularization of Java applications. A module is a self-contained piece of code that represents a single unit of functionality. It is a higher-level concept than a package, which is a collection of related classes and interfaces.

A module consists of three main parts:

Module Declaration: This is a file named module-info.class or module-info.java that defines the module's name, dependencies, and exports (more on this later). The module declaration specifies the module's structure and its relationships with other modules.

Module Graph: This is a directed graph that represents the relationships between modules. Each module is an node in the graph, and the edges represent the dependencies between them. A module can depend on zero or more other modules. Module Contents: These are the classes, interfaces, and other types declared within the module.

The main features of a Java module are:

Exports: A module can export its contents to other modules. This means that the exported contents can be accessed from outside the module, but only by modules that depend on it. Requires: A module can require other modules as dependencies. If a module depends on another, it must have access to all the exported contents of that module. Provides: A module can provide services or APIs to other modules.

The benefits of using modules in Java include:

Improved code organization and structure Better dependency management Enhanced security through fine-grained control over what is exposed to outside modules Easier maintenance and upgrading of individual modules

To create a Java module, you need to follow these steps:

Create a new directory for your module. Write the module declaration file (module-info.class or module-info.java) that defines the module's name, dependencies, and exports. Add the necessary files (e.g., source code, resources) to the module directory. Compile the module using the Java compiler (javac). Run the module using the Java runtime (java).

In conclusion, a Java module is a self-contained unit of functionality that provides better organization, dependency management, and security for your Java applications.

What is a module system in Java?

I apologize, but as per the RULES, I shall respond in Simplified Chinese: