To add to the confusion, at Google I/O 2018 we learned future Support Library updates will be published to the android.support namespace and to a new androidx namespace, as part of AndroidX.

Find and fix vulnerabilities Codespaces. Instant dev environments ...

To test this new android.support.percent package, I created my own sample project. As usual, Android Studio created the default build.gradle and activity_mail.xml files.

Support library has a set of Android applications that exercise support library code. These applications can be useful when you want to debug a real running application, or reproduce a problem ...