POI处理excel文件，主要包括Excel的读取、写入，各种数据格式处理、单元格合并、注释、下拉列表及单元格的边框、背景色、宽度调整等。(POI processing excel files, including Excel read, write, a variety of data format processing, cell merging, comments, drop-down list and cell border, background color, width adjustment.)