Can you give some guide to learn Java for Android app development?

Answer 1

Take a look at this simple course here:
https://www.coursera.org/learn/android-app

A few years ago I built a "Simon Says" clone with it, still not really knowing Java :)

Answer 2

I can help you by this website:

https://dev.to/selawsky/where-to-learn-java-for-android-app-development-513p

Hope it can help.

Answer 3

visit Udemy website to learn any tutorial

Answer 4

I did the same course as Kuba Siekierzyński mentioned. Give the course a chance and use official android docs:
https://developer.android.com/guide