How is Holden an outsider in the book, The Catcher in the Rye?

Holden throughout the novel neither is able to mix/
desolve himself up with the society he is in despite of different attempt nor does he
can leave his ideology. he doesnot enjoy anything at all except the presence of Phoeb
and Alley and Jane( who come in his memory) he is indifferent to almost everything
around him. thus he can be conscidered outsider in this novel.