What is a good way to punish a 4 year old?

Me and my girlfriend are 23 years old and we have a 4 year old son. Yes me and my girlfriend are his real parents...So the thing is that he is a really hyper kid and doesnt listen to us at all sometimes. She gets really frustrated and sometimes punishes him too harshly I think. Sometimes she just locks him up in the bathroom for like an hour. Is it a good way to punish him or is there a better way??