we have to use:
For handling .xls files, we use HSSF (Horrible SpreadSheet Format) related POI classes.
For handling .xlsx files, we use XSSF (XML SpreadSheet Format) related POI classes.
On this post, how we can perform excel operations with one set code for both excel formats .xls and .xlsx.
For this we have a class provided from Apache POI WorkbookFactory, which auto detects appropriate kind of Workbook (HSSFWorkbook or XSSFWorkbook) depending on the excel formats .xls or .xlsx.
Let's jump to the code implementation