Apache POI
Apache POI is a Java library for reading and writing Microsoft Office file formats, such as Excel (.xls, .xlsx), Word (.doc, .docx), PowerPoint (.ppt, .pptx), and Outlook (.msg). It provides APIs to manipulate these documents programmatically, enabling developers to create, modify, and extract data from Office files without requiring Microsoft Office to be installed. The library supports both the older binary formats (e.g., .xls) and the newer XML-based formats (e.g., .xlsx) introduced in Office 2007 and later.
Developers should learn Apache POI when building Java applications that need to generate reports, import/export data, or automate document processing involving Microsoft Office files, such as in enterprise systems, data analysis tools, or business automation workflows. It is particularly useful for scenarios like creating Excel spreadsheets from database queries, parsing Word documents for content extraction, or generating PowerPoint presentations dynamically, as it offers fine-grained control over file structures and content.