
I made a Java module out of the ANTLRv4 runtime, and made it into a
modular jar, as follows:

Started with antlr-runtime-4.4.jar, downloaded from antlr.org.

mkdir antlr4runtime
cd antlr4runtime
cp /path/to/antlr-runtime-4.4.jar .
tar xf antlr-runtime-4.4.jar

Create file module-info.java with this contents:

module antlr.runtime {
    exports org.antlr.v4.runtime;
    exports org.antlr.v4.runtime.atn;
    exports org.antlr.v4.runtime.dfa;
    exports org.antlr.v4.runtime.misc;
    exports org.antlr.v4.runtime.tree;
    exports org.antlr.v4.runtime.tree.pattern;
}

javac -d . --module-path . module-info.java

This created module-info.class.    Get rid of module-info.java....
mv module-info.java ..
cd ..
jar --create --file=antlr4runtime.jar -C antlr4runtime .

Now you have a module named antlr4runtime which can be used in other
modular Java projects via this jar.
