concept module declaration in category java

This is an excerpt from Manning's book The Java Module System. Login to get full access to this book.

The only thing you need to do is add a file called module-info.java, a module declaration, to your source folder and fill it with your module’s name, dependencies on other modules, and the packages that make up its public API:

Figure 2.4 Each module of the ServiceMonitor application is its own project with the well-known directory structure. New are the mods folder, which collects the modular JARs once they’re built, and the module declarations module-info.java file in each project’s root source directory.

> monitor.observer/src/main/java/monitor-observer-info.java:1:
>     error: module declarations should be in a file named module-info.java
> module monitor.observer {
> ^
> 1 error

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What I like best, though, are the module declarations themselves: they’re at all times a true representation of your project’s architecture and will provide considerable benefits to every developer and architect who works on those aspects of their system, thus improving its overall maintainability. (I go deeper into this topic in section 15.2.3.)