Create New Workbook

Apache POI SS

Workbook wb = new HSSFWorkbook();

FileOutputStream fileOut;
fileOut = new FileOutputStream("newWorkbook.xls");
wb.write(fileOut);
fileOut.close();

Aspose.Cells

Workbook workbook = new Workbook(); // Creating a Workbook object
workbook.save("newWorkBook.xlsx", FileFormatType.XLSX); //Workbooks can be saved in many formats

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