Java9: Welcome to Module world

Java 9 has been released on September 21 officially, Eclipse is supporting Java 9 from  Eclipse Oxygen.1a (4.7.1a), Lets jump into module world..!!!

Download Java 9 from here, and add it to Eclipse Installed JRE’s as below

That’s it, we are good to write Java 9 module programs in Eclipse.

1. Create First java project and add module-info.java to it, right click on the project

module-info.java

module first {

}

Module should start with keyword module followed by its name. currently it doesn’t requires anything or it doesn’t export anything.

2. Let’s create Second java project,

module-info.java

module second {
exports second; --<em> second module is exporting a package "second"</em>
}

Second.java — create a simple Java class with public sayHello() method in second package

package second;

public class Second {
public void sayHello() {
System.out.println("Welcome to module world..!!");
}
}

Second java class will be available to other modules, as it is exporting second package.

3. Update first module –  module-info.java as below

module first {
requires second;
}

Now first module requires second module, but it will fail with module can not be resolved compilation error

“second cannot be resolved to a module”

we need to add second module as dependency to first module.

Check the new thing called modulepath

3. Create FirstTest.java in first package as below

package first;

import second.Second; // we are accessing Second.java from second module

public class FirstTest {

public static void main(String[] args) {
Second second = new Second();
second.sayHello();
}
}

Running the above would print “Welcome to module world..!!”

source code can be found at Github