java HSSFCell 导入获取时间

导入Excel的时候，后台java获取cell时间的时候，转换成了数字，该方法是把数字转换成时间类型的字符串

public static String getCell(HSSFCell cell) {
DecimalFormat df = new DecimalFormat("#");
if (cell == null)
return "";
switch (cell.getCellType()) {
case HSSFCell.CELL_TYPE_NUMERIC:
if(HSSFDateUtil.isCellDateFormatted(cell)){
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
return sdf.format(HSSFDateUtil.getJavaDate(cell.getNumericCellValue())).toString();
}
return df.format(cell.getNumericCellValue());
case HSSFCell.CELL_TYPE_STRING:
System.out.println(cell.getStringCellValue());
return cell.getStringCellValue();
case HSSFCell.CELL_TYPE_FORMULA:
return cell.getCellFormula();
case HSSFCell.CELL_TYPE_BLANK:
return "";
case HSSFCell.CELL_TYPE_BOOLEAN:
return cell.getBooleanCellValue() + "";
case HSSFCell.CELL_TYPE_ERROR:
return cell.getErrorCellValue() + "";
}
return "";
}