XSSFSheet

XSSFSheet is a class in the Apache POI library that represents a single worksheet within an XSSF workbook, the implementation POI uses for the OOXML-based .xlsx format. It is the XSSF-specific counterpart to the HSSFSheet class used for .xls files. XSSFSheet implements the Sheet interface and is typically accessed through an XSSFWorkbook. A sheet contains rows, which in turn contain cells, and it provides mechanisms to create, retrieve, and remove these rows and cells, as well as to manage sheet-wide properties such as column widths, merged regions, and print settings.

Common usage patterns involve creating a workbook, adding a sheet with workbook.createSheet("Name"), then creating rows with sheet.createRow(0) and cells with row.createCell(0). Values are assigned via cell.setCellValue(...) with support for numeric, string, boolean, and date types. Styles can be applied using cell.setCellStyle(...). The sheet supports operations like merging regions with addMergedRegion(CellRangeAddress) and querying or enumerating merged regions. Other typical operations include retrieving rows with getRow(int) and iterating through rows and cells.

Under the hood, XSSFSheet delegates to XSSFRow and XSSFCell, which map to the underlying OOXML structures (such as CTWorksheet and related XML components). Changes to a sheet are held in memory and only written to the underlying .xlsx file when the workbook is written. This class is designed for use within the single-process lifecycle of constructing or modifying an in-memory workbook before writing it out.

Compared with HSSFSheet, XSSFSheet targets the newer XLSX format and supports larger data capacity and OOXML-specific styling. It is generally intended to be used in a single-threaded context or with proper synchronization during construction of the workbook.