Adding multiple sheets in Excel (apache POI)

Hello everyone,

Just want to ask for suggestions where I can add multiple sheets in one .xls file

Currently, I have 3 individual 'reports' with their own respective report generator class.

Apple (sheet name) --> 1.xls
Banana ---> 2.xls
Carrot ---> 3.xls

Let's say I already have an existing sheet for 'Apple' and have already generated a report for it. On the next scenario, what would I like to do is create a sheet where 'Apple' existed (1.xls) without overwriting the file itself, thus making 1.xls include Apple sheet and Banana sheet at the same time.

On the latter, those 3 sheets should only be located in one file.