private static CTWorksheet newSheet(){
CTWorksheet worksheet = CTWorksheet.Factory.newInstance();
CTSheetFormatPr ctFormat = worksheet.addNewSheetFormatPr();
ctFormat.setDefaultRowHeight(15.0);
CTSheetView ctView = worksheet.addNewSheetViews().addNewSheetView();
ctView.setWorkbookViewId(0);
worksheet.addNewDimension().setRef("A1");
worksheet.addNewSheetData();