C.T.Co Trainee Java Developer interview questions

The hiring process took almost 45 days including Saturdays and Sundays. Which was kind of long period despite the fact it was in summer when people want to travel etc. and not to sit and home and wait for potential invite for an interview. First thing that was needed is to send regular CV + motivation letter, after that got a call from HR representative who conducted phone interview and then invited for group interview (around 8 candidates) + 2 HR specialists. Negative impression was left as there was only 2 questions per person and was feeling that you told only 1/10 about yourself/skills/experience etc. Anyways got further, received technical task on e-mail and was told that need to send completed tasks (3 algorithmic programs) after 3 days from task receival date. In requirements it was mentioned and was followed that you can use any programming language, as in position requirements there was mentioned: Basic knowledge of any programming language. So task was sent for review, and some time later got invitation for technical interview. And here begins the most interesting part. Instead of checking basic things, interviewer asked specific Java language questions, including Java Collections API. As well as question about String immutability and String as object itself. As I understood afterwards got rejected due to fact that when got asked about Collections API, I have misplaced two data structures, but at the end corrected those by myself, but still this question was rated as unanswered according to HR feedback. All this process was kind of difficult for Trainee position and with requirement "basic" knowledge of "any" programming language, but in reality specific questions about Java programming language.