Can a guy and a girl in their early 20's be "just friends"?

There is this guy that I use to work with (in different departments) and i had a little crush on him and he would always stare at me and then look away and not make eye contact. He finally got the courage and started a conversation with me one day. And we just clicked and had great chemistry. And for a couple of weeks he would always seek me out to talk to me and we would go on lunch breaks together. One day he mentions to me that he has a GF! to say I was shocked would be an understatement, but I got over it and figured he doesn't owe me anything. Well months went by and he continued to be really flirty and he rarely speaks about his GF to me. He always compliments me and teases me and tries to lightly touch me any chance he gets. He is also always really interested to know about my private life like if I like anybody at the moment and or if I am seeing anyone because I am "so attractive" there has been chances where his Gf has been around but he wont introduce me to her? And now that I wont be seeing him much because of new jobs he says we have to catch up? I am just confused from his signals. I have come to the conclusion that he just wants to be friends. But I have friends telling me that he likes me and it will be impossible for us to simply be friends because a guy who is truly happy in his relationship will not go out and pay attention to another girl?