poi excel 加粗

参考 https://blog.csdn.net/wellto/article/details/52293202

XSSFWorkbook xwb = new XSSFWorkbook();

...

XSSFCell cell
...

XSSFFont font1 = xwb.createFont();

font1.setBold(true);

XSSFCellStyle style1 = xwb.createCellStyle();

style1.setFont(font1);

cell.setCellStyle(headerStyle);