计算两个日期相差多少天

/**
 * 计算两个日期相差多少天
 */
public class TestDate {

    public static void main(String[] args)throws ParseException  {
        System.out.println("你来世界的天数: "+daysBetween("2000-05-10","2020-11-13"));
    }

    /**
     *字符串的日期格式的计算
     */
    public static int daysBetween(String smdate,String bdate) throws ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Calendar instance = Calendar.getInstance();
        instance.setTime(sdf.parse(smdate));
        long time1 = instance.getTimeInMillis();

        instance.setTime(sdf.parse(bdate));
        long time2 = instance.getTimeInMillis();

        long between_days = (time2 - time1) / (1000 * 3600 * 24);

        return Integer.parseInt(String.valueOf(between_days));
    }

    /**
     *字符串的日期格式的计算
     */
    public static int daysBetween(Date smdate, Date bdate) throws ParseException {
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        Calendar instance = Calendar.getInstance();
        instance.setTime(smdate);
        long time1 = instance.getTimeInMillis();

        instance.setTime(bdate);
        long time2 = instance.getTimeInMillis();

        long between_days = (time2 - time1) / (1000 * 3600 * 24);

        return Integer.parseInt(String.valueOf(between_days));
    }
}