IBM Software Engineer interview questions

There were lots of coding items in the written test for 1 hr. First part is multiple choice. About Java threading and memory management. Second part is the coding. Most items are using arraylist. I was not able to finish the exam so during the interview they asked me how did I arrived with my answers. I felt I was able to answer them well or convinced them with my answers but I was wrong to assume on that. I made a follow up if I passed. Unfortunately, I receive the confirmation that they will not proceed further with my application.