Is it possible to build an operating system for Raspberry Pi with Java?

Answer 1

Yes, but you are better of trying to create an OS using C/C++. There are a lot of custom criteria that need to be met when building an operating system, such as registries, basic I/O, public interface, etc.
Hope that I could answer your question, friend!

Answer 2

Yes, but it's probably not the best language for an OS and you will need a runtime which obviously isn't written in Java. https://en.m.wikipedia.org/wiki/JavaOS

Btw. randomly mentioning codes here won't help you at all :)

Answer 3

Oh yes tanks