Apache POI Features

Apache POI (Poor Obfuscation Implementation File System) provides stream-based processing which is useful for large files and takes less memory.
It is helpful to handle both XLS and XLSX formats of spreadsheets.
This library contains HSSF implementation for Excel (97-2007) file format i.e .xls.
The XSSF library implementation should be used for Excel .xlsx file format.
The HSSF library and XSSF API provides mechanisms to read, write or modify excel spreadsheets.
It also provides SXSSF that is an extension of XSSF to work with very large excel sheets.
The SXSSF requires less memory and is suitable when working with very large spreadsheets.
Apache POI provides excellent support for additional excel features such as working with Formulas, creating cell styles by filling colors and borders, fonts, headers and footers, data validations, images, hyperlinks etc.