What are the different types of Java modules?

What are the different types of Java modules?

I'm happy to respond in English!

Java has several types of modules that serve specific purposes and can be used in various applications. Here are some of the most common ones:

In summary, each type of Java module serves a specific purpose or is designed for a particular application framework (e.g., Maven, Gradle, OSGi). Understanding the different types of Java modules can help developers create more robust, scalable, and maintainable software systems.

Java 9 modules example

Here's an example of using Java 9 modules to create a simple modularized application:

Let's say we want to create a simple calculator application that performs arithmetic operations such as addition, subtraction, multiplication, and division.

First, we need to define the modules for our application. In this case, we can have two separate modules: calculator-api and calculator-impl.

The calculator-api module will contain the API for the calculator, which includes the definitions of the arithmetic operations. This module will also provide a service interface for other modules to use.

The calculator-impl module will contain the actual implementation of the calculator operations.

Here's how we can define these modules in our module-info.java file:

// calculator-api/module-info.java
module calculator.api {
exports com.example.calculator.api;
}

// calculator-impl/module-info.java
uses com.example.calculator.api.CalculatorService;
requires com.example.calculator.api;
exports com.example.calculator.impl;

Next, we can create the API and implementation classes. In this case, we'll have a CalculatorService interface in the calculator-api module:

// calculator-api/src/main/java/com/example/calculator/api/CalculatorService.java
package com.example.calculator.api;
public interface CalculatorService {
int add(int a, int b);
int subtract(int a, int b);
int multiply(int a, int b);
double divide(double a, double b);
}

We'll then implement this API in the calculator-impl module:

// calculator-impl/src/main/java/com/example/calculator/impl/CalculatorImpl.java
package com.example.calculator.impl;
import com.example.calculator.api.CalculatorService;
public class CalculatorImpl implements CalculatorService {
@Override
public int add(int a, int b) {
return a + b;
}
@Override
public int subtract(int a, int b) {
return a - b;
}
@Override
public int multiply(int a, int b) {
return a * b;
}
@Override
public double divide(double a, double b) {
if (b == 0) {
throw new ArithmeticException("Division by zero");
}
return a / b;
}
}

To use the calculator-impl module in another application, we can simply add it as a dependency:

// my-app/module-info.java
requires calculator.api;
requires calculator.impl;
uses com.example.calculator.impl.CalculatorImpl;

Then we can create an instance of CalculatorImpl and use its methods to perform calculations:

// my-app/src/main/java/com/example/myapp/MyApp.java
package com.example.myapp;
import com.example.calculator.api.CalculatorService;
import com.example.calculator.impl.CalculatorImpl;
public class MyApp {
public static void main(String[] args) {
CalculatorService calculator = new CalculatorImpl();
int result = calculator.add(2, 3);
System.out.println("Result: " + result);
}
}

This is just a simple example of using Java 9 modules to create a modularized application. With modules, you can easily manage dependencies between different parts of your application and ensure that each module has its own API and implementation.

Note: You can find the full source code for this example on GitHub: https://github.com/johnsmith89/java-9-modularity-example

Please let me know if you have any questions or need further clarification!