Do too many subquries create multiple sleeping processes in MySQL?

I am using java & MySQL to make an app. When I check the process list. I see a lot of sleeping processes. It also reaches to a points when no further connection is allowed. I have read many answers around which tell the command to masskill the process or some suggests checking the code for bug. I have checked that I'm closing the connections properly using the Apache Commons DbUtils. DbUtils.closeQuietly(rs); DbUtils.closeQuietly(statement); DbUtils.closeQuietly(con); I am not able to figure out why these processes don't get killed after closing the connection. My question is 1. Do too many subquries create multiple sleeping processes in MySQL? I don't see much relation though and didn't find anything on search. 2. Does passing connection object through methods create extra/multiple processes? Regards