ZonedDateTime format() method in Java with Examples

The format() method of ZonedDateTime class in Java is used to format this date-time using the specified formatter passed as parameter.This date-time will be passed to the formatter to produce a string.

Syntax:

public String format(DateTimeFormatter formatter)

Parameters: This method accepts a single parameter formatter which represents the formatter to use. This is a mandatory parameter and should not be NULL.

Return value: This method returns a String represents the formatted date-time string.

Exception: This method throws a DateTimeException if an error occurs during printing.

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

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

import java.time.*;
import java.time.format.*;

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

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

        // create a formatter
        DateTimeFormatter formatter = DateTimeFormatter.ISO_TIME;

        // apply format()
        String value = zoneddatetime.format(formatter);

        // print result
        System.out.println("Result: " + value);
    }
}

Output:

Result: 19:21:12.123+05:30

Program 2:

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

import java.time.*;
import java.time.format.*;

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

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

        // create a formatter
        DateTimeFormatter formatter = DateTimeFormatter.BASIC_ISO_DATE;

        // apply format()
        String value = zoneddatetime.format(formatter);

        // print result
        System.out.println("Result: " + value);
    }
}

Output:

Result: 20181025+0200

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