private void setCellStyle(Sheet sheet, int rowIndex, int cellIndex, CellStyle style){
if(style == null) return;
Row row = sheet.getRow(rowIndex);
if(row == null) row = sheet.createRow(rowIndex);
Cell cell = row.getCell(cellIndex);
if(cell == null) cell = row.createCell(cellIndex);
if(cell.getCellStyle() == null || (cell.getCellType() != Cell.CELL_TYPE_NUMERIC)
|| (!DateUtil.isCellDateFormatted(cell))
|| DateUtil.isADateFormat(style.getDataFormat(), style.getDataFormatString()))
cell.setCellStyle(style);
else{