ZonedDateTime withNano() method in Java with Examples

withNano() method of a ZonedDateTime class used to alter nano-of-second in this ZonedDateTime and return a copy of ZonedDateTime after this operation.This method operates on the local time-line, changing the time of the local date-time and after this operation local date-time is converted back to a ZonedDateTime, using the zone ID to obtain the offset. When converting back to ZonedDateTime, if the local date-time is in an overlap, then the offset will be retained if possible, otherwise, the earlier offset will be used. This instance is immutable and unaffected by this method call.

Syntax:

public ZonedDateTime withNano(int nanoOfSecond)

Parameters: This method accepts a single parameter nanoOfSecond which represents the nano-of-second to set in the result, 0 to 999, 999, 999.

Return value: This method returns a ZonedDateTime based on this date-time with the requested nanoOfSecond.

Exception: This method throws DateTimeException if the nanoOfSecond value is invalid.

Below programs illustrate the withNano() method:
Program 1:

// Java program to demonstrate
// ZonedDateTime.withNano() method

import java.time.*;

public class GFG {
    public static void main(String[] args)
    {

        // create a ZonedDateTime object
        ZonedDateTime zoneddatetime
            = ZonedDateTime.parse(
                "2018-12-06T19:21:12.123+05:30[Asia/Calcutta]");

        // print instance
        System.out.println("ZonedDateTime before"
                           + " alter nanoOfSecond: "
                           + zoneddatetime);

        // alter nanoOfSecond to 12345987
        ZonedDateTime returnvalue
            = zoneddatetime.withNano(12345987);

        // print result
        System.out.println("ZonedDateTime after "
                           + "alter nanoOfSecond: "
                           + returnvalue);
    }
}

Output:

ZonedDateTime before alter nanoOfSecond: 2018-12-06T19:21:12.123+05:30[Asia/Calcutta]
ZonedDateTime after alter nanoOfSecond: 2018-12-06T19:21:12.012345987+05:30[Asia/Calcutta]

Program 2:

// Java program to demonstrate
// ZonedDateTime.withNano() method

import java.time.*;

public class GFG {
    public static void main(String[] args)
    {

        // create a ZonedDateTime object
        ZonedDateTime zoneddatetime
            = ZonedDateTime.parse(
                "2018-10-25T23:12:31.123+02:00[Europe/Paris]");

        // print instance
        System.out.println("ZonedDateTime before"
                           + " alter nanoOfSecond: "
                           + zoneddatetime);

        // alter nanoOfSecond to 439990000
        ZonedDateTime returnvalue
            = zoneddatetime.withNano(439990000);

        // print result
        System.out.println("ZonedDateTime after "
                           + "alter nanoOfSecond: "
                           + returnvalue);
    }
}

Output:

ZonedDateTime before alter nanoOfSecond: 2018-10-25T23:12:31.123+02:00[Europe/Paris]
ZonedDateTime after alter nanoOfSecond: 2018-10-25T23:12:31.439990+02:00[Europe/Paris]

Reference: https://docs.oracle.com/javase/10/docs/api/java/time/ZonedDateTime.html#withNano(int)