ZonedDateTime withHour() method in Java with Examples

withHour() method of a ZonedDateTime class used to alter hour-of-day 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 withHour(int hour)

Parameters: This method accepts a single parameter hour which represents the hour-of-day to set in the result, from 0 to 23.

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

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

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

// Java program to demonstrate
// ZonedDateTime.withHour() 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 hour: "
                           + zoneddatetime);

        // alter hour to 20
        ZonedDateTime returnvalue
            = zoneddatetime.withHour(20);

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

Output:

ZonedDateTime before alter hour: 2018-12-06T19:21:12.123+05:30[Asia/Calcutta]
ZonedDateTime after alter hour: 2018-12-06T20:21:12.123+05:30[Asia/Calcutta]

Program 2:

// Java program to demonstrate
// ZonedDateTime.withHour() 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 hour: "
                           + zoneddatetime);

        // alter hour to 0
        ZonedDateTime returnvalue
            = zoneddatetime.withHour(0);

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

Output:

ZonedDateTime before alter hour: 2018-10-25T23:12:31.123+02:00[Europe/Paris]
ZonedDateTime after alter hour: 2018-10-25T00:12:31.123+02:00[Europe/Paris]

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