使用easypoi的MultipartFile来上传多个文件，报数组下标异常

//controller层的代码
 public R importExcel(@RequestBody MultipartFile[] files) throws Exception {
        ImportParams params = new ImportParams();
      //设置表头的行数
        params.setHeadRows(1);
        params.setStartSheetIndex(2);
        params.setSheetNum(1);
        List<ElecRegionGdp> importExcelList = 
       ExcelImportUtil.importExcel(files[0].getInputStream(), ElecRegionGdp.class, params);
        elecRegionGdpService.impRegionGDPData(importExcelList);
        return R.ok("导入成功");
    }

//service层的代码 
public void impRegionGDPData(List<ElecRegionGdp>compareList) throws Exception{
        for (ElecRegionGdp compare : compareList) {//elecResionGDP是实体的gdp表
            ElecRegion region = new ElecRegion();//eleResion是实体
            region.setName(compare.getRegionName());
            List<ElecRegion> regions = regionService.findListByEntity(region);
            if (!V.isEmpty(regions)) {
                region = regions.get(0);
                compare.setRegionId(region.getId());
                compare.setRegionIds(region.getPids());
            }
            this.add(compare);
        }