//开始行，结束行，开始列，结束列
sheet.addMergedRegion(new CellRangeAddress(0, 0, 0, 3));
HSSFRow row = sheet.createRow(0);
HSSFCell cellHeader;
cellHeader = row.createCell(0);
//cellHeader.setCellStyle(style);
cellHeader.setCellValue("标题...");
向大家推荐《Activiti工作流实战教程》:https://xiaozhuanlan.com/activiti