private void setBordersToMergedCells(XSSFWorkbook workBook, XSSFSheet sheet) {
int numMerged = sheet.getNumMergedRegions();
for(int i= 0; i<numMerged;i++){
CellRangeAddress mergedRegions = sheet.getMergedRegion(i);
RegionUtil.setBorderTop(CellStyle.BORDER_THIN, mergedRegions, sheet, workBook);
RegionUtil.setBorderLeft(CellStyle.BORDER_THIN, mergedRegions, sheet, workBook);
RegionUtil.setBorderRight(CellStyle.BORDER_THIN, mergedRegions, sheet, workBook);
RegionUtil.setBorderBottom(CellStyle.BORDER_THIN, mergedRegions, sheet, workBook);
}
}