Who was Robert Ackley?

Robert Ackley is Holden's unpleasant dormmate, whose personal habits are dirty and whose room stinks. Holden suspects that Ackley does not brush his teeth and describes them as mossy. Cursed with acne, Ackley constantly picks at the sores. Ackley dislikes Stadlater, calling him a "son of a bitch." Holden finds Ackley disgusting but appears to feel sorry for him at the same time.