private static void createCase6(String filename) throws IOException {
HSSFWorkbook wb = new HSSFWorkbook();
HSSFSheet sheet1 = wb.createSheet("new sheet");
sheet1.groupColumn(2, 10);
sheet1.groupColumn(4, 10);
sheet1.setColumnGroupCollapsed(4, true);
sheet1.setColumnGroupCollapsed(2, true);
sheet1.setColumnGroupCollapsed(3, false);