输入两个日期得出相差的月份

public class demo {
    public static void main(String[] args) throws ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM");
        String str1 = "2017-06";
        String str2 = "2017-01";
        Date date = new Date();
        String format = format.format(date);     
        Calendar a = Calendar.getInstance();
        Calendar aft = Calendar.getInstance();
        a.setTime(format.parse(str1));
        b.setTime(format.parse(str2));
        int result = b.get(Calendar.MONTH) - a.get(Calendar.MONTH);
        int month = (b.get(Calendar.YEAR) - a.get(Calendar.YEAR)) * 12;
        System.out.println(Math.abs(month + result));
    }
}