Merging Two excel files as two sheets in one workbook in java

Question

I have two xlsx files at folder C:\DemoFilesExcel\demo1.xlsx and C:\DemoFilesExcel\demo2.xlsx.

I want to create a new xlsx C:\DemoFilesExcel\merged.xlsx that will have these two files as two sheets in merged.xlsx workbook.

This is to be done using apache POI in java. Any idea how to do