This is a tough question, because in The Catcher in the Rye you could make the case that Holden doesn't change much at all. Really, he's a critic of society (but not of himself) throughout the entire novel. In the end, he regrets telling us his story at all, which shows that he is very conservative and in denial of change and maturity. In short, he's a reluctant hero not ready to cross the threshold into the adult, illegitimate world.
If I had to choose only three (3) ways in which he changes, it would be:
1) He doesn't commit suicide, like James Castle. Because of Antolini's advice ("The mark of a mature man is that he lives for [a noble cause]"), Holden refuses to romanticize his own death. He refuses to martyr himself for the phony culture.
2) Holden refuses to enter that adult world of sex. He hires the prostitute Sonny only to talk to her. In short, he wants to protect his and her innocence. By losing his virginity, he might have been swallowed up and drowned in the adult world completely.
3) Holden chooses to live for Phoebe, his sister, instead of kill himself for Allie, his brother who died of leukemia. Holden lives with survivor's guilt, and he can't turn to adults for help. So, he looks to become a surrogate parent to his little sister, a type of therapy and a noble cause.
Holden Caulfield has changed his perspectives in few areas; he alters his attitude about Mr. Antolini, his sister Phoebe, and his writing of his autobiographical account.
In Chapter 24 when Holden visits his former teacher, Mr. Antolini is very solicitous and suggests gently that he thinks Holden is "riding for some kind of terrible fall." But because it is late and Holden feels extremely sleepy, Holden cannot listen well to the good advice that Mr. Antolini gives him. So, his host makes up the couch as a bed for Holden.
After sleeping for a while, Holden wakes up and discovers Mr. Antolini stroking his head. He is very upset by this. Since he claims to have had "that kind of stuff" happen before, Holden believes that Mr. Antolini is gay.
Later, in Chapter 25, Holden rethinks what has occurred with Mr. Antolini:
...I wondered if just maybe I was wrong about thinking he was making a flitty pass at me. I wondered if maybe he just liked to pat guys on the head when they're asleep.... I mean I started thinking that even if he was a flit, he certainly'd been very nice to me.
Whereas Holden has desired to be a "catcher in the rye" and save children from the phoniness of adulthood as a protector of their innocence in Chapter 24, in Chapter 25, he changes his mind.
In Chapter 25 Holden sends Phoebe a message to meet him at the museum, where he will return her Christmas money, which she gave him. When she arrives, Phoebe has a suitcase with her and asks if she can go with him. Holden denies her request, instructing her to return to school, but Phoebe adamantly refuses to go, so he offers to take her to the zoo. There the siblings reconcile and Holden convinces Phoebe to ride the carousel as she has in the past. As Holden sits watching her, he sees Phoebe grab for the gold ring, and he becomes afraid that she will be hurt. But, Holden recognizes,
The thing with kids is, if they want to grab for the gold ring, you just have to let them do it, and not say anything. If they fall off, they fall off, but it's bad if you say anything to them.
Thus, Holden realizes that he cannot stop children from maturing. He cannot be "a catcher in the rye."
--His autobiographical account
After giving his account of why he has left school and his feelings about phonies and other people and things, Holden reveals that he has been institutionalized for a while, but he will soon attend a new school. However, he does not want to reveal much more, and he wishes now that he had not told so much about himself already. He adds,
Don't ever tell anybody anything. If you do, you start missing everybody.