Can I be able to design apps by learning java ?

Answer 1

1--First learn Java...........
2--Work hard ...........
3--Keep yourself motivated........

Refer to this :

https://www.sololearn.com/Course/Java/?ref=app

Answer 2

If you're only looking to design apps, then you can look into

UX/UI Design Software

If you actually want the apps to function, then yes you'll need to learn Java or any other programming language that meets your needs.