java实现两个date算出相差天数

测试代码：

        String dateStr1 = "2022-5-17";
        String dateStr2 = "2022-5-05";
        SimpleDateFormat format1 = new SimpleDateFormat("yyyy-MM-dd");
        SimpleDateFormat format2 = new SimpleDateFormat("yyyy-MM-dd");
        try {
            Date date1 = format1.parse(dateStr1);
            Date date2 = format2.parse(dateStr2);

            System.out.println("相差了："+differentDays(date1,date2)+"天！");
            System.out.println(differentDayMillisecond(date1,date2));
        } catch (ParseException e) {
            e.printStackTrace();
        }

differentDays实现代码：

 public static int differentDays(Date date1,Date date2){
        Calendar calendar1 = Calendar.getInstance();
        calendar1.setTime(date1);
        Calendar calendar2 = Calendar.getInstance();
        calendar2.setTime(date2);

        int day1 = calendar1.get(Calendar.DAY_OF_YEAR);
        int day2 = calendar2.get(Calendar.DAY_OF_YEAR);
        int year1 = calendar1.get(Calendar.YEAR);
        int year2 = calendar2.get(Calendar.YEAR);

        if (year1 != year2)  //不同年
        {
            int timeDistance = 0;
            for (int i = year1 ; i < year2 ;i++){ //闰年
                if (i%4==0 && i%100!=0||i%400==0){
                    timeDistance += 366;
                }else { // 不是闰年
                    timeDistance += 365;
                }
            }
            return  timeDistance + (day2-day1);
        }else{// 同年
            return day2-day1;
        }

    }