What does it mean if a guy puts his hands in his pockets?

I've noticed that sometimes my crush puts his hands in his pockets when he sees me. He doesn't do it all the time, but he has done it a couple times. Does this mean anything or am I just reading too much into nothing? He usually avoids eye contact with me when he does this which gives me the idea he might be nervous.
What does it mean if a guy puts his hands in his pockets?
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