Selected for Ninja Interview

Hey folks, please guide me with this interview, please do let me know what are the possible technical stuff a Ninja candidate can be asked by the interviewer, it is on 27th this month, I'm literally nervous about this.

I was expecting a prime role but due to lack of understanding and knowledge, irrespective of writing the whole code right, I couldn't figure out that I have to use a scanner for taking inputs from the compiler, because of which my both the codes irrespective of being correct didn't qualify me for the prime role but instead got a Ninja role.

Please help me with the last minute prep, my core language is java