Holden Caulfield is largely self-defined in The Catcher in the Rye according to his many likes and dislikes. His nervous state is expressed in his hyper-opinionated personality. There are many, many opinions put forth by Holden and some of these provide significant insight into the turmoil of his character.
Early in the novel, Holden expresses his dislike for situations where he does not have a chance to get a real good-bye. Being kicked out of as many schools as he has, Holden is used to departure but he strongly prefers a formal end to things.
"I don't care if it's a sad good-by or a bad good-by, but when I leave a place I like to know I'm leaving it."
We can connect this opinion to the death of Holden's younger brother Allie.
Holden also says that he likes Jesus but dislikes the disciples. Jesus, in Holden's opinion, made all the sacrifices while the disciples did nothing until after Jesus' death. No one helped Jesus when he needed help and Holden holds that against the disciples.
This set of opinions relates to Holden's fixation on integrity. Many of his likes and dislikes have to do with integrity, as he likes the people who demonstrate conviction and honesty despite the circumstances and dislikes those who change in beliefs and behavior according to the situation. His brohter D.B. is a nice example of the way Holden groups people into two categories based on integrity.
When D.B. is writing his stories, he is alright in Holden's mind, but when he goes to Hollywood to write movies D.B. is a phony.