如果前后仅5分钟，如何舍入到最接近的小时? [英] How to round off to the closest hour if its only 5 minutes ahead or behind?

问题描述

我想在Java中将 Instant 舍入到最接近的小时，但前提是它在最接近的小时的5分钟之内.

I want to round off an Instant to its closest hour in Java, but only if it's within 5 minutes of the closest hour.

假设时间是:2021-02-08T19:02:49.594
预期结果:2021-02-08T19:00:00.000

Suppose the time is: 2021-02-08T19:02:49.594
Expected result: 2021-02-08T19:00:00.000

同样，如果时间是:2021-02-08T19:56:49.594
预期结果:2021-02-08T20:00:00.000

Similarly, if the time is: 2021-02-08T19:56:49.594
Expected result: 2021-02-08T20:00:00.000

但是如果时间是2021-02-08T19:54:49.594或2021-02-08T19:06:49.594，那么什么也不做.

But if the time is 2021-02-08T19:54:49.594 or 2021-02-08T19:06:49.594 then do nothing.

推荐答案

您可以简单地检查日期时间的分钟部分，然后根据需要将其截断为小时.

You can simply check the minute part of the date-time and truncate it to hours as per the requirement.

演示:

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.time.temporal.ChronoUnit;

class Main {
    public static void main(String[] args) {
        // Test
        String[] arr = { "2021-02-08T19:02:49.594", "2021-02-08T19:56:49.594", "2021-02-08T19:54:49.594",
                "2021-02-08T19:06:49.594" };

        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("uuuu-MM-dd'T'HH:mm:ss.SSS");

        for (String s : arr) {
            System.out.println(roundToNearestHour(s).format(dtf));
        }
    }

    static LocalDateTime roundToNearestHour(String str) {
        LocalDateTime ldt = LocalDateTime.parse(str);
        int minute = ldt.getMinute();
        return minute < 5 ? ldt.truncatedTo(ChronoUnit.HOURS)
                : (minute >= 55 ? ldt.plusHours(1).truncatedTo(ChronoUnit.HOURS) : ldt);
    }
}

输出:

2021-02-08T19:00:00.000
2021-02-08T20:00:00.000
2021-02-08T19:54:49.594
2021-02-08T19:06:49.594

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