https://blog.csdn.net/weixin_45156610/article/details/105433804


cellStyle.setAlignment(HorizontalAlignment.CENTER);
cellStyle.setVerticalAlignment(VerticalAlignment.CENTER);
cellStyle.setBorderBottom(BorderStyle.THIN);
cellStyle.setBottomBorderColor(HSSFColor.HSSFColorPredefined.BLACK.getIndex());
cellStyle.setBorderLeft(BorderStyle.THIN);
cellStyle.setLeftBorderColor(HSSFColor.HSSFColorPredefined.BLACK.getIndex());
cellStyle.setBorderRight(BorderStyle.THIN);
cellStyle.setRightBorderColor(HSSFColor.HSSFColorPredefined.BLACK.getIndex());
cellStyle.setBorderTop(BorderStyle.THIN);
cellStyle.setTopBorderColor(HSSFColor.HSSFColorPredefined.BLACK.getIndex());