Oracle Senior Software Developer interview questions

Interview Scheduled by company they took only one round most of the question is coming form project they asked flow of project in brief regarding my module how it is working, what are the difficulty i m faced in this module how to resolved those issue he ask me to write some code also related to my project and also their scenario etc. after that they ask me collection related questions how HashMap internally working write your own LinkedHashMap why HashSet data is not preserved etc.