Java 9+ is not supported on Android, so if you want to link to a Java 9+ library for an Android application, your only path is to rewrite it in Kotlin, as it is clear from this announcement that Google won't bother to add the required machinery to ART to support Java 9+ class files and new libraries.

Naturally the other alternative would be to downgrade the code back to Java 8, but then the question remains for how long they will keep it around.

Might have less to do with users and more to do with Oracle v Google