Glassfish Example

Here is a real example of some code that does that, namely Glassfish 4.1 does not run on JDK nine because the JVM throws an IllegalAccessError
The error message is

class  com.sun.enterprise.security.provider policy wrapper 

in module unnamed module, cannot access class

com.sun.security.provider policy file 

in module java.base.
Now a glance at the open JDK repository shows us that the policy file class in sun.security is declared public, but because that package is not exported by java.base, policy file is only accessible from code in java.base itself.

I would like to return to the

module-info.java

file that declares the HelloWorld module.
It is really important to understand that a module

1. exports packages,
2. but requires modules.

The reason is due to an old software engineering principle. The "unit of reuse" is the "unit of release".