Phoniness, hypocrisy, and Deceit are common themes present in "The Catcher in the Rye"
"If you want to know the truth, I don't know why I started all that stuff with her. I mean about going away somewhere, to Massachusetts and Vermont and I probably wouldn't've taken her even if she wanted to go with. The terrible part, though, is that I meant it when I asked her. That's the terrible part. I swear to God I'm a madman"(pg149).
"That annoyed me for some reason. "Oh Christ. Don't spoil it," I said. "I'm twelve for chrissake. I'm big for my age"(pg 81).
"Hey--How old are you, anyhow?"(pg 81).
"It isn't very serious. I have this tiny little tumor on the brain"(pg 65). "Then I started reading this timetable I had in my pocket. Just to stop lying. Once I get started, I can go on for hours if I feel like it. No kidding. Hours"(pg 65).
Holden mentions his hatred for phony's but he was a hypocrite because he often lies and is very deceitful.
He lies to the girl in the bar about his age when they are dancing and gets annoyed when she asks. He was being a phony.
He was talking to the mother of a kid from Pencey named Ernest Morrow and among many other lies told on the train that night, he lied about having a tumor.