Structure

Whole project is organize by their package, the main functional can known by package name.

com.app.walper - All Activity Class placed
com.app.notch.adapter - Adapter for ViewPager, ListView, Image List etc
com.app.notch.connection - All class related REST API request
com.app.notch.data - The supporting data like, config, constant
com.app.notch.fragment - Fragment page placed here
com.app.notch.fcm - FCM notification Handler
com.app.notch.model - All Object Model placed
com.app.notch.room - Room Database located
com.app.notch.utils - Internet detector, callback class, and snippet

RENAME PACKAGE

We are NOT recommend you to rename your physical package, because it will cause a lot of error. If you want to upload into google play you only need to change applicationId at gradle file, here the tutorial how to rename package http://blog.dream-space.web.id/?p=62