--创建单元格
WritableCell cell = new Label(colIndex, rowIndex, value == null ? "" : value.toString(), format);
WritableCellFeatures ft = new WritableCellFeatures();
--设置批注内容
ft.setComment("这里填写批注内容");
--给单元格设置批注
cell.setCellFeatures(ft);
sheet.addCell(cell);
思考:如何实现任意列设置批注?