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The format() method of LocalDateTime class in Java formats this date-time using the specified formatter. Syntax:

public String format(DateTimeFormatter formatter)

Parameter: This method accepts a parameter formatter which specifies the formatter to use, not null. Returns: The function returns the formatted date string and not null. Below programs illustrate the LocalDateTime.format() method: Program 1:

Java

// Java program to illustrate the format() method

import java.util.*;
import java.time.*;
import java.time.format.DateTimeFormatter;

public class GfG {
    public static void main(String[] args)
    {
        // Parses the date
        LocalDateTime dt1
            = LocalDateTime
                  .parse("2018-11-03T12:45:30");

        // Prints the date
        System.out.println("Original LocalDateTime: "
                           + dt1);

        // Display d1 in different formats
        // using format() method
        System.out.println("BASIC_ISO_DATE format: "
                           + (DateTimeFormatter.BASIC_ISO_DATE)
                                 .format(dt1));
        System.out.println("ISO_LOCAL_DATE format: "
                           + (DateTimeFormatter.ISO_LOCAL_DATE)
                                 .format(dt1));
        System.out.println("ISO_DATE format: "
                           + (DateTimeFormatter.ISO_DATE)
                                 .format(dt1));
        System.out.println("ISO_LOCAL_TIME format: "
                           + (DateTimeFormatter.ISO_LOCAL_TIME)
                                 .format(dt1));
        
    }
}

Output:

Original LocalDateTime: 2018-11-03T12:45:30
BASIC_ISO_DATE format: 20181103
ISO_LOCAL_DATE format: 2018-11-03
ISO_DATE format: 2018-11-03
ISO_LOCAL_TIME format: 12:45:30

Program 2:

Java

// Program to illustrate the format() method

import java.util.*;
import java.time.*;
import java.time.format.DateTimeFormatter;

public class GfG {
    public static void main(String[] args)
    {
        // Parses the date
        LocalDateTime dt1
            = LocalDateTime
                  .parse("2016-09-06T12:45:30");

        // Prints the date
        System.out.println(dt1);

        // Display d1 in different formats
        // using format() method
        System.out.println("ISO_TIME format: "
                           + (DateTimeFormatter.ISO_TIME)
                                 .format(dt1));
        System.out.println("ISO_LOCAL_DATE_TIME format: "
                           + (DateTimeFormatter.ISO_LOCAL_DATE_TIME)
                                 .format(dt1));
        System.out.println("ISO_DATE_TIME format: "
                           + (DateTimeFormatter.ISO_DATE_TIME)
                                 .format(dt1));
        System.out.println("ISO_ORDINAL_DATE format: "
                           + (DateTimeFormatter.ISO_ORDINAL_DATE)
                                 .format(dt1));
        System.out.println("ISO_WEEK_DATE format: "
                           + (DateTimeFormatter.ISO_WEEK_DATE)
                                 .format(dt1));
    }
}

Output:

2016-09-06T12:45:30
ISO_TIME format: 12:45:30
ISO_LOCAL_DATE_TIME format: 2016-09-06T12:45:30
ISO_DATE_TIME format: 2016-09-06T12:45:30
ISO_ORDINAL_DATE format: 2016-250
ISO_WEEK_DATE format: 2016-W36-2

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

LocalDateTime format() method in Java

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