Question

我有一个有时间的字符串。我需要把它四舍五入到最近的小时和最近的一分钟。我怎么在java中做到这一点？例如：字符串时间=“12:58:15”; 我需要把它四舍五入到1:00:00和12:58:00

Answer 1

对于日历操作，您必须使用Calendar类。在你的情况下，你会做这样的事情：

package test;

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;

public class TestDate {

    public static void main(String[] args) {
        Calendar c = new GregorianCalendar();
        c.set(Calendar.HOUR_OF_DAY, 12);
        c.set(Calendar.MINUTE, 58);
        c.set(Calendar.SECOND, 15);
        Date d = c.getTime();

        System.out.println("Start point: " + d.toString());
        System.out.println("Nearest whole minute: " + toNearestWholeMinute(d));
        System.out.println("Nearest whole hour: " + toNearestWholeHour(d));
    }

    static Date toNearestWholeMinute(Date d) {
        Calendar c = new GregorianCalendar();
        c.setTime(d);

        if (c.get(Calendar.SECOND) >= 30)
            c.add(Calendar.MINUTE, 1);

        c.set(Calendar.SECOND, 0);

        return c.getTime();
    }

    static Date toNearestWholeHour(Date d) {
        Calendar c = new GregorianCalendar();
        c.setTime(d);

        if (c.get(Calendar.MINUTE) >= 30)
            c.add(Calendar.HOUR, 1);

        c.set(Calendar.MINUTE, 0);
        c.set(Calendar.SECOND, 0);

        return c.getTime();
    }

}

结果：

Start point: Tue Nov 22 12:58:15 CET 2011
Nearest whole minute: Tue Nov 22 12:58:00 CET 2011
Nearest whole hour: Tue Nov 22 13:00:00 CET 2011

Answer 2

一种方法是首先使用SimpleDateFormat及其解析方法将其转换为日期（javadoc将解释您需要的格式）。然后你可以查看秒数并确定你应该上升一分钟还是下降（如果它上升，将秒数设置为0并添加一分钟）。同样地，对于小时，只要看几分钟，如果它小于30，则向下舍入，如果大于30，则设置为零并增加小时。

Answer 3

在Java 8中，您可以使用java.time.LocalDateTime或ZonedDateTime（时区）。可以四舍五入到最接近的小时数：

String mytime = "2019-05-21 13:41:50";

// Convert String to LocalDateTime
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
LocalDateTime localDateTime = LocalDateTime.parse(mytime, dtf);

// If minutes equals 30 or more, add 1 hour
int minutes = localDateTime.getMinute();
if (minutes >= 30)
{
    localDateTime = localDateTime.plusHours(1);
}

// Round down
localDateTime = localDateTime.truncatedTo(ChronoUnit.HOURS)

// Back to String (OP wants the end result to be of type String)    
String roundedTime = dtf.format(localDateTime);
System.out.println(roundedTime);

例如："2019-05-21 13:41:50"将被打印为2019-05-21 14:00:00

Answer 4

使用SimpleDateFormat创建日期。从日期创建GregorianCalendar。将分钟或秒数滚动30。然后将分钟或秒设置为0.

Answer 5

package com.xyz.util;

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;

public class DateTimeUtils {

    public static void main(String[] args) {
        Date date = new Date();
        date.setHours(23);
        System.out.println("prev whole hour, millies: "+toWholeHour(date,-1)+", "+toWholeHour(date,-1).getTime());
        System.out.println("curr whole hour, millies: "+toWholeHour(date,0)+", "+toWholeHour(date,0).getTime());
        System.out.println("next whole hour, millies: "+toWholeHour(date,1)+", "+toWholeHour(date,1).getTime());

        System.out.println("prev whole minute, millies: "+toWholeMinute(date,-1)+", "+toWholeMinute(date,-1).getTime());
        System.out.println("curr whole minute, millies: "+toWholeMinute(date,0)+", "+toWholeMinute(date,0).getTime());
        System.out.println("next whole minute, millies: "+toWholeMinute(date,1)+", "+toWholeMinute(date,1).getTime());
    }

    public static Date toWholeHour(Date d, int beforeOrAfter) {
        Calendar c = new GregorianCalendar();
        c.setTime(d);
        c.add(Calendar.HOUR, beforeOrAfter);
        c.set(Calendar.MINUTE, 0);
        c.set(Calendar.SECOND, 0);
        c.set(Calendar.MILLISECOND, 0);
        return c.getTime();
    }

    public static Date toWholeMinute(Date d, int beforeOrAfter) {
        Calendar c = new GregorianCalendar();
        c.setTime(d);
        c.add(Calendar.MINUTE, beforeOrAfter);
        c.set(Calendar.SECOND, 0);
        c.set(Calendar.MILLISECOND, 0);
        return c.getTime();
    }

}

Answer 6

嗯，最好的答案是最简单的答案

  /**
   * 2020-01-01 10:00:55 is transformed into 2020-01-01 10:00:00
   * 2020-01-01 10:20:55 is transformed into 2020-01-01 10:00:00
   * 2020-01-01 10:30:01 is transformed into 2020-01-01 11:00:00
   * @return the Timestamp rounded to the nearest hour
   */
  public static Timestamp roundTimestampToNearestHour(Timestamp input){
    return Timestamp.from(Instant.ofEpochMilli(((input.getTime()+1800000)/(60000*60))*(60000*60)));
}

在java中我们如何将时间四舍五入到最近的小时和分钟？

6 个答案: