private static void printYearMonth(String start, String end) throws Exception {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Date s = sdf.parse(start);
        Date e = sdf.parse(end);
        Calendar cals = Calendar.getInstance();
        cals.setTime(s);
        Calendar cale = Calendar.getInstance();
        cale.setTime(e);
        StringBuffer sb = new StringBuffer();
        while (cals.before(cale)) {
            sb.append(sdf.format(cals.getTime()));
            sb.append("至");
            cals.set(Calendar.DATE, 1);
            cals.add(Calendar.MONTH, 1);
            if (cals.after(cale)) {
                cals = cale;
                sb.append(sdf.format(cals.getTime()) + "\n");
                break;
            }
            cals.add(Calendar.DATE, -1);
            sb.append(sdf.format(cals.getTime()) + "\n");
            cals.add(Calendar.DATE, 1);

        }
        System.out.print(sb.toString());
    }