Assuming that each of your arena implementations extend Arena, then no, you don't need a cast or an instanceof check.
Again I recommend that you use a Map to String, Arena and return that. You do not need to cast or instance check, just return whatever...
I highly recommend that you use only one ArenaManager. Store your arenas in a collection of <Arena> since all of your subtypes extend that...
we're gonna have another 1k liked very soon
Good for debugging, poor for production code. See http://stackoverflow.com/questions/299068/how-slow-are-java-exceptions:...
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