Create New Module System in Java 9

Environment Setup

Using Eclipse Oxygen and JDK 9

Create Calculator Module

The steps below show how to create a new module

Create a new Java Project in Eclipse

Provide Project Name is com.calculator and select JRE

Create module descriptor: Right click on project and go to Configure > Create module-info.java

Input module descriptor name is com.operators

Structure of project after adding module descriptor

Code inside module descriptor

module com.operators {

	exports com.operators;

}

Create com.operators package

Add Operators class as below:

package com.operators;

public class Operators {

	public int add(int a, int b) {
		return a + b;
	}

	public int sub(int a, int b) {
		return a - b;
	}

	public int mul(int a, int b) {
		return a * b;
	}

}

Add Main class as below:

package com.operators;

public class Main {

	public static void main(String[] args) {

	}

}

Structure of project after adding Operators class

Run and export module

Right click on project and go to Run As > Java Application

Test Calculator Module

The steps below show how to test calculator module

Create a new Java Project in Eclipse

Provide Project Name is MyClientTest and select JRE

Add calculator module to test project: Right click on project and go to Build Path > Configure Build Path

In Project tab select Modulepath. Click Add button and select com.calculator module

After add calculator module

Create com.demo package in test project

Create module descriptor: Right click on project and go to Configure > Create module-info.java

Input module descriptor name is com.demo

Code inside module descriptor

module com.demo {

	requires com.operators;

}

Create com.demo package and create Main class inside com.demo package

Run test project

package com.demo;

import com.operators.Operators;

public class Main {

	public static void main(String[] args) {

		Operators operators = new Operators();
		System.out.println("Add: " + operators.add(10, 2));
		System.out.println("Sub: " + operators.sub(10, 2));
		System.out.println("Sub: " + operators.mul(10, 2));

	}

}

Output

Add: 12
Sub: 8
Mul: 20