algorithm grouping

i am perplexing assistance someone way i guess easy, nonetheless impetus never :)

i am perplexing take category register (usually between 10-20 students) effectivly singly camber off any classmate another unparalleled groups. therefore category 10 people, have 9 groups.

it needs means hoop rare array students too, adding confusion.

i looking during doing java, nonetheless flexible. any ideas an algorithmic proceed pledge a)not enormous looping (ending 2 have already partners) b) i am aiming some-more efficent space, given category distance small!

thanks!