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  • java的系统时间,怎么计算从现在到凌晨还剩下多少时间?

    Apache commons-lang3

    long milliSecondsLeftToday = 86400000 - 
        DateUtils.getFragmentInMilliseconds(Calendar.getInstance(), Calendar.DATE);

    System.currentTimeMillis() 是零时区的时间戳,所以你要加上8个小时才行。
    最基础的写法:

    public class Main {
        public static void main(String[] args) {
            long hour = 60 * 60 * 1000;
            long time = System.currentTimeMillis();
            System.out.println(time);
            time += 8 * hour; 
            System.out.println(time);
            time %= 24 * hour;
            System.out.printf("%02d:%02d
    ", time / hour, time % hour / 60000);
            time = 24 * hour - time;
            System.out.printf("%02d:%02d
    ", time / hour, time % hour / 60000);
        }
    }

    在当前时区有夏令时的情况下,另外一个用System.currentTimeMillis() 的答案是不能正确处理的,比如15年美国夏令时从3月8号凌晨2点开始,如果现在时间是3月8号1点,那种方式计算出来的就是错误的,而Calendar API可以正确处理,虽然很难用。

    Calendar c = Calendar.getInstance();
    long now = c.getTimeInMillis();
    
    c.add(Calendar.DAY_OF_MONTH, 1);
    c.set(Calendar.HOUR_OF_DAY, 0);
    c.set(Calendar.MINUTE, 0);
    c.set(Calendar.SECOND, 0);
    c.set(Calendar.MILLISECOND, 0);
    
    long millis = c.getTimeInMillis() - now;

    Java8中的写法

    LocalTime midnight = LocalTime.MIDNIGHT;
    LocalDate today = LocalDate.now();
    LocalDateTime todayMidnight = LocalDateTime.of(today, midnight);
    LocalDateTime tomorrowMidnight = todayMidnight.plusDays(1);
    System.out.println(TimeUnit.NANOSECONDS.toSeconds(Duration.between(LocalDateTime.now(), tomorrowMidnight).toNanos()));

    https://www.zhihu.com/question/28475461



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  • 原文地址:https://www.cnblogs.com/softidea/p/7188416.html
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