If this is what you care about, then ask questions that lead the interviewee to demonstrating knowledge of these skills. Demonstrating skill with functional-is

If this is what you care about, then ask questions that lead the interviewee to demonstrating knowledge of these skills. Demonstrating skill with functional-ish "stream" APIs means the developer is a lot more likely to understand any impl's built on functional paradigms (e.g. Spark, actors, etc.), or at least can pick them up very quickly since the APIs and semantics are quite similar. A candidate who writes list.stream().filter(...).map(...).collect(...) gets big bonus points in my book. I'll ask them about efficiency, to see if they know when to drop to for-loops. If they write a 1.4 for-loop, I'll ask them to evolve or parallelize it to see if, at some point, they stop adding complexity to their loop and instead switch to a cleaner functional style. Starting from a for-loop and asking to implement some simple transformations like filters, reverse, group by, map, etc., does wonders to separate the wheat from the chaff here.