holli gave you a complete, working, OO-based program with reusable modules at Re: Split file based on tag in response to your Split file based on tag. You previously had answers at file split, print line, and delete line.

If for some reason (teacher, boss, lack of OO knowledge, etc.) you cannot use holli's excellent solution to your problem, you should at least have been able to extract the techniques you need from that code.

Now please do as holli suggested here: Re^3: Split file based on tag.