How to tell difference between flirting or being friendly?

Last week I was in training for a job. I met a guy named jordan. I ended up working with him tonight. He introduced himself and forgot to send in his order when he first met me. Then he stared at me the next day. Tonight I was talking to a guy I worked with. Jordan said I was a hater I turned around to see him staring at me. I said what do you mean I'm a hater you don't even know me. Cause I didn't even talk to him...all my coworkers were messing with me. He started to sing "are you gonna be my girl" cause the song was on the radio wasnt singing any of the rest. 2 guys who helped me out tonight said something to him but I couldn't hear what they were saying..he was probably just being nice to me introducing himself and over thinking stuff. He also asked me out of everyone there if he had coffee on his sleeves. Which was weird cause he thought he had it on his back of the sleeves. The guy I talked to most of the night told me how if someone always talks to themselves means they have a high iq. Jordan jumped into our convo randomly and was on my side that it made him sound stupid since he heard it from a tv show