Porting Java code from PC to other platforms?

Question

linux

I know that it is painlessly transferred to PC platforms. But on other platforms ( Andorid ), do you need to rewrite the entire application from the platform API?
Prompt cross-platform libraries on java.

Answer 1

1) What is the main platform?
2) What is the development language?
You can universally answer something like this ... Logic is easily transferred, the main thing is that there is a compiler of your language for the target platform. Any interactions with the platform API - either you need to immediately write on something universal and broadcastable (Qt), or write your own interaction with the API on each platform.