Round by next quarter minutes always

We have a requirement to Round by next quarter minutes in Java code, for example:

1. if current date time is 2020-05-28T10:01:00
   then, round up to next quarter to make it 2020-05-28T10:15:00

2. if current date time is 2020-05-28T10:15:01
   then, round up to next quarter to make it 2020-05-28T10:30:00

3. if current date time is 2020-05-28T10:46:15
   then, round up to next quarter to make it 2020-05-28T11:00:00

4. if current date time is 2020-12-31T23:47:00
   then, round up to next quarter to make it 2021-01-01T00:00:00

Can someone please provide Java code to achieve this. Any help is appreciated.

Tried below code but unable to get the output which I'm looking for:

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

    public class Main {
        public static void main(String[] args) {
            Calendar calendar = Calendar.getInstance();
            calendar.setTime(new Date());
            int round = calendar.get(Calendar.MINUTE) % 15;
            calendar.add(Calendar.MINUTE, round < 8 ? -round : (15-round));
            calendar.set( Calendar.SECOND, 0 );
            System.out.println(calendar.getTime());
        }
    }

This can be easily done using the LocalDateTime class from the java.time package, which you should be using anyway¹.

public static LocalDateTime roundUpToQuarter(LocalDateTime datetime) {
    int minutesToAdd = 15 - (datetime.getMinute() % 15);
    return datetime
        .plusMinutes(minutesToAdd)
        .truncatedTo(ChronoUnit.MINUTES);
}

This calculation involving the modulus operator makes sure that we get the number of minutes to add to go to the next full quarter. The truncatedTo(ChronoUnit.MINUTES) call makes in turn sure that all fields smaller than 'minutes' are set to zero.

Update: I'm not certain of your exact use case, but, as Basil pointed out, if you want to represent a moment on the timeline, then you also need a timezone or offset. This can be done by replacing LocalDateTime instances with ZonedDateTime in the abovementioned method.

¹ The Date, Calendar and SimpleDateFormat classes are obsolete. They may work in simple cases, but they will cause trouble in more complex cases. See https://stackoverflow.com/questions/1969442/whats-wrong-with-java-date-time-api.

You can try below code.

    Calendar calendar = Calendar.getInstance();
    calendar.setTime(new Date(1609438620000l));
    int fraction = calendar.get(Calendar.MINUTE) / 15;
    switch (fraction) {
    case 0: {
        calendar.set(Calendar.MINUTE, 0);
        break;
    }
    case 1: {
        calendar.set(Calendar.MINUTE, 15);
        break;
    }
    case 2: {
        calendar.set(Calendar.MINUTE, 30);
        break;
    }
    default: {
        calendar.set(Calendar.MINUTE, 45);
        break;
    }
    }
    calendar.add(Calendar.MINUTE, 15);
    calendar.set(Calendar.SECOND, 0);
    System.out.println(calendar.getTime());