Apache POI Cheat Sheet
Apache POI is the de-facto Java library for reading and writing Microsoft Office documents. The link below jumps straight to the official quick guide covering both the old HSSF (BIFF8/XLS) and newer XSSF (OOXML/XLSX) APIs.
Recommended Reference
Quick Tips
- Use
WorkbookFactory.create(InputStream)
when you need to support both XLS and XLSX without branching. - Close
SXSSFWorkbook
instances explicitly to flush temporary files when writing large spreadsheets. - Validate cell formats before exporting sensitive financial data; Excel silently truncates decimals if format strings are incorrect.
Maintenance Note
Always pin your project to a supported POI version—older releases packaged in legacy apps can contain security vulnerabilities (CVE-2019-12415, CVE-2021-36090). Review the Apache POI release notes before upgrading production systems.