code: private static void setCellStyle(SheetTemplate template, Cell cell, String styleKey) {
          if (null != styleKey && null != template.classifyStyle.get(styleKey)) {
              cell.setCellStyle(template.classifyStyle.get(styleKey));
              return;
          }
  
          if (null != template.appointLineStyle && template.appointLineStyle.containsKey(cell.getRowIndex())) {
              cell.setCellStyle(template.appointLineStyle.get(cell.getRowIndex()));
              return;
          }
          if (null != template.singleLineStyle && (cell.getRowIndex() % 2 != 0)) {
              cell.setCellStyle(template.singleLineStyle);
              return;
          }
          if (null != template.doubleLineStyle && (cell.getRowIndex() % 2 == 0)) {
              cell.setCellStyle(template.doubleLineStyle);
              return;
          }
          if (null != template.defaultStyle)
              cell.setCellStyle(template.defaultStyle);
      }
docs: 设置某个元素的样式
  
  @param cell     cell元素
  @param styleKey 样式标识