For interviews, should I practice problems in Objective-C or some other language?

So I'm studying up for technical interview problems and I've been doing all the practice problems in Java instead of Objective-C or Swift. I did this for a few reasons:1). Java is a more mainstream language than Objective-C (but still object oriented) 2). All the practice problems are in Java but I haven't seen any in Objective-C 3). I've done a fair amount of Android programming so I'm comfortable in it

What do you think? Should I be doing these in Objective-C even though it might be a bit more cumbersome? I had an interviewer last week for an iOS position who wasn't on the iOS team but just wanted to know my technical chops so we did everything in Java.