docs: private void setCellType(Attributes attribute) {
  		// 重置numFmtIndex,numFmtString的值
  		numFmtIndex = 0;
  		numFmtString = "";
  		this.cellDataType = CellDataType.of(attribute.getValue(T_ATTR_VALUE));
  
  		// 获取单元格的xf索引，对应style.xml中cellXfs的子元素xf
  		final String xfIndexStr = attribute.getValue(S_ATTR_VALUE);
  		if (xfIndexStr != null) {
  			int xfIndex = Integer.parseInt(xfIndexStr);
  			XSSFCellStyle xssfCellStyle = stylesTable.getStyleAt(xfIndex);
  			numFmtIndex = xssfCellStyle.getDataFormat();
  			numFmtString = xssfCellStyle.getDataFormatString();
  
  			if (numFmtString == null) {
  				cellDataType = CellDataType.NULL;
  				numFmtString = BuiltinFormats.getBuiltinFormat(numFmtIndex);
  			} else if (org.apache.poi.ss.usermodel.DateUtil.isADateFormat(numFmtIndex, numFmtString)) {
  				cellDataType = CellDataType.DATE;
  			}
  		}
  
  	}