📄️ Workbook
In Apache POI, a Workbook represents the entire Excel file.
📄️ Sheet
A Sheet represents a single tab inside an Excel workbook.
📄️ Row
A Row represents a horizontal line of cells in a sheet.
📄️ Cell
A Cell represents a single value inside a row.
📄️ Object Model & Indexing Rules
Apache POI follows a strict hierarchy:
📄️ Null Handling Strategy
In Apache POI: