how does mr antolini represent holdens feelings and experiences with adults

This about comes it up. This has everything to do with Holden's view of the hypocrisy and "fakeness" of adults in general,

Mr. Antolini had married an older woman who shared similar intellectual interests. When he arrives at his apartment, Holden finds Mr. Antolini in a bathrobe and slippers, drinking a highball. Holden and Mr. Antolini discuss Pencey, and Holden tells how he failed Oral Expression (debate). He tells Holden how he had lunch with his father, who told him that Holden was cutting classes and generally unprepared. He warns Holden that he is riding towards some kind of terrible fall. He says that it may be the kind where, at the age of thirty, he sits in some bar hating everyone who comes in looking as if he played football in college or hating people who use improper grammar. Furthermore, he tells Holden that the fall that he is riding for is a special and horrible kind, and that he can see Holden dying nobly for some highly unworthy cause.

He gives Holden a quote from the psychoanalyst Wilhelm Stekel: "The mark of the immature man is that he wants to die nobly for a cause, while the mark of the mature man is that he wants to live humbly for one." He finally tells Holden that once he gets past the things that annoy him, he will be able to find the kind of information that will be dear to his heart. Holden goes to sleep, and wakes up to find Mr. Antolini's hand on his head. He tells Holden that he is "simply sitting here, admiring" but Holden interrupts him, gets dressed and leaves, claiming that he has to get his bags from Grand Central Station and will be back soon.