Question: why is holden worried about jane and stradlater?
Answer: Holden is "nervous" about Stradlater going out with Jane because he knows Stradlater all too well. He is quite sure that Stradlater will do his best to seduce Jane, as he does with every girl he takes out on a date. Holden uses the term "nervous," but actually he feels jealous, possessive, and protective.