JavaModulesImplementation.md

Java Module example

1. Create a project - C:\..\modulesDemo
2. Create a folder for java files under the project - src\com.aj.modules
3. Create a the java module file in the directory src\com.aj.modules - module-info.java

module com.aj.modules {
}

4. Create the folder for file to be included in the module - src\com.aj.modules\com\aj\modules
5. Create TestMain.java file

package com.aj.modules;

public class TestMain {
	
	public static void main (String args[]) {
		System.out.println("Hello modules from medium :)");
	}
}

6. Create a folder to store the module compiled files - ../modulesDemo/mods/com.aj.modules
7. Before compilation folder structure

../modulesDemo
      ├── mods
            └── com.aj.modules
      └── src
	    └── com.aj.modules
	    	├── module-info.java
              	└── com
                  └── aj
                    └── modules
                      └── TestMain.java

8. Compile the module, navigate to the project folder i.e. modulesDemo, and compile the module using the command below.

javac -d mods/com.aj.modules src/com.aj.modules/module-info.java`

Command explaination-
<-d mods/com.aj.modules> - output directory
<src/com.aj.modules/module-info.java> - source directory

9. Compile the module contents i.e. TestMain.java file. javac -d mods/com.aj.modules src/com.aj.modules/com/aj/modules/TestMain.java
10. After the compilation you will have a project structure as below

../modulesDemo
      ├── mods
            └── com.aj.modules
              ├── module-info.class
              └── com
                └── aj
                  └── modules
                    └── TestMain.class
      └── src
            └── com.aj.modules
	      ├── module-info.java
              └── com
                └── aj
                  └── modules
                    └── TestMain.java

11. To run the TestMain class in the module, navigate to folder /modulesDemo, the run this command-

java --module-path mods -m com.aj.modules/com.aj.modules.TestMain

Command explaination-
java --module-path <path to module, compiled> -module <module name>/<package>.<main class>

12. Here is the output-

C:\..\modulesDemo>java --module-path mods -m com.aj.modules/com.aj.modules.TestMain
Hello modules from medium :)