At the time of research, Samsara offered the only dormbeds in Karimunjawa, although the folks at The Coconut House are building a new guesthouse that will offer dorms too.
Ten six - beddorms (8 mixed, two female - only) line the length of the longhouse block facing a small yard with not one, but two smallish swimming pools (although we only saw one), split by an all - day bar (yep, 24/7).