*/
public XSSFSheet createSheet(String sheetname) {
if (containsSheet( sheetname, sheets.size() ))
throw new IllegalArgumentException( "The workbook already contains a sheet of this name");
CTSheet sheet = addSheet(sheetname);
int sheetNumber = 1;
for(XSSFSheet sh : sheets) sheetNumber = (int)Math.max(sh.sheet.getSheetId() + 1, sheetNumber);
XSSFSheet wrapper = (XSSFSheet)createRelationship(XSSFRelation.WORKSHEET, XSSFFactory.getInstance(), sheetNumber);
wrapper.sheet = sheet;
sheet.setId(wrapper.getPackageRelationship().getId());
sheet.setSheetId(sheetNumber);
if(sheets.size() == 0) wrapper.setSelected(true);
sheets.add(wrapper);
return wrapper;
}