How to tell if a stoic, introverted guy likes you?

Well, there's someone that I like but he'll never talk to me and he'll just look at me when he thinks I am not aware. I don't know what he's thinking but others also say that he looks like a high self-esteem guy. Since I know his personality, I don't really think so. He's mostly not associated with girls and not have much friends tho. But he's quite ambitious. Please help me figure out what kind of guy he is
How to tell if a stoic, introverted guy likes you?
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