Specification for "java.lang.module" states that
"Unless otherwise noted, passing a null argument to a constructor or method of any class or interface in this package will cause a NullPointerException to be thrown."

This is not always so for ModuleReader instances. Consider the following code sample:

=====================
import java.io.IOException;
import java.lang.module.ModuleFinder;
import java.lang.module.ModuleReader;

public class InstalledNONPE {

    public static void main(String[] args) {
        ModuleFinder.ofSystem().findAll().stream().forEach(mref -> {
            try {
                mref.open().open((String) null);
                mref.open().read((String) null);
                System.out.println("No NPEs");
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        });
    }
}
=====================

No NPEs will be seen in the output.

The following JCK tests fail due to this problem

api/java_lang/module/ModuleReader/index.html#InstalledModules[open_NPE]
api/java_lang/module/ModuleReader/index.html#InstalledModules[read_NPE]
api/java_lang/module/ModuleReader/Generic/test.html[release_NPE]