Apache POI Java API for Microsoft Documents

create and maintain Java APIs for manipulating various file formats based upon the Office Open XML standards (OOXML) and Microsoft's OLE 2 Compound Document format (OLE2). In short, you can read and write MS Excel files using Java. In addition, you can read and write MS Word and MS PowerPoint files using Java. Apache POI is your Java Excel solution (for Excel 97-2008). We have a complete API for porting other OOXML and OLE2 formats and welcome others to participate

http://poi.apache.org/spreadsheet/quick-guide.html

New Workbook Workbook wb = new HSSFWorkbook();
FileOutputStream fileOut = new FileOutputStream("workbook.xls");
wb.write(fileOut);
fileOut.close();
Workbook wb = new XSSFWorkbook();
FileOutputStream fileOut = new FileOutputStream("workbook.xlsx");
wb.write(fileOut);
fileOut.close();

New Sheet Workbook wb = new HSSFWorkbook();
//Workbook wb = new XSSFWorkbook();
Sheet sheet1 = wb.createSheet("new sheet");
Sheet sheet2 = wb.createSheet("second sheet");
FileOutputStream fileOut = new FileOutputStream("workbook.xls");
wb.write(fileOut);
fileOut.close();

Creating Cells Workbook wb = new HSSFWorkbook();
//Workbook wb = new XSSFWorkbook();
CreationHelper createHelper = wb.getCreationHelper();
Sheet sheet = wb.createSheet("new sheet");
// Create a row and put some cells in it. Rows are 0 based.
Row row = sheet.createRow((short)0);
// Create a cell and put a value in it.
Cell cell = row.createCell(0);
cell.setCellValue(1);
// Or do it on one line.
row.createCell(1).setCellValue(1.2);
row.createCell(2).setCellValue(
createHelper.createRichTextString("This is a string"));
row.createCell(3).setCellValue(true);
// Write the output to a file
FileOutputStream fileOut = new FileOutputStream("workbook.xls");
wb.write(fileOut);
fileOut.close();