Holden has a really big problem with growing up, and he really wants to escape it. In the book, he keeps saying that adults are phonies, and he keeps saying flaws about them, on the contrary, the only people he says good things about are kids, for example, Phoebe, Allie, and the little boy that sings the song about the catcher in the rye. Also, he is always trying to make plans to escape growing up, for example, working on a ranch out West. You can clearly see that he likes kids not adults, when he states he wants to be a catcher in the rye when he grows up (catching children before they fall of a cliff). This is a symbol for trying to save kids from growing up and become like adults.
SEXUAL CONFUSION
It is normal for adolescents to feel confused about sex, and that is what Holden is going through. Holden is going through the normal part of life in which you have curiosity and start feeling the urge of having sexual intercourse, but the problem is that he doesn't know how to respond to the feeling.
ALIENATION
Alienation is a big theme in The Catcher in the Rye, because Holden keeps alienating himself from the rest of the world for self-protection. Holden truly believes he is protecting himself, since he is not making any kind of connection, so nobody will ever be able to hurt him. He keeps pushing people out, so he becomes very lonely, and this is the main reason for his instability throughout the novel.