LocalDateTime withDayOfYear() method in Java with Examples

The withDayOfYear() method of LocalDateTime class in Java is used to get a copy of this LocalDateTime with the dayOfYear changed to the dayOfYear passed as the parameter to this method. The remaining values of this LocalDateTime remains the same.

Syntax:

public LocalDateTime withDayOfYear(int dayOfYear)

Parameter: This method accepts a single mandatory parameter dayOfYear which specifies the dayOfYear to be set in the resultant LocalDateTime instance. The value of this dayOfYear can range from 1 to 366.

Returns: The function returns a LocalDateTime instance with the dayOfYear changed to the dayOfYear passed as the parameter to this method. The remaining values of this LocalDateTime remains the same.

Exceptions: The function throws a DateTimeException if the dayOfYear value is invalid.

Below programs illustrate the LocalDateTime.withDayOfYear() method:

Program 1:

// Program to illustrate the withDayOfYear() method

import java.util.*;
import java.time.*;

public class GfG {
    public static void main(String[] args)
    {
        // Get the LocalDateTime instance
        LocalDateTime dt = LocalDateTime.now();

        // Get the String representation of this LocalDateTime
        System.out.println("Original LocalDateTime: "
                           + dt.toString());

        // Get a new LocalDateTime with dayOfYear 1
        System.out.println("New LocalDateTime: "
                           + dt.withDayOfYear(1));
    }
}

Output:

Original LocalDateTime: 2018-11-30T12:54:35.320
New LocalDateTime: 2018-01-01T12:54:35.320

Program 2:

// Program to illustrate the withDayOfYear() method

import java.util.*;
import java.time.*;

public class GfG {
    public static void main(String[] args)
    {
        // Get the LocalDateTime instance
        LocalDateTime dt
            = LocalDateTime
                  .parse("2015-04-06T10:15:30");

        // Get the String representation of this LocalDateTime
        System.out.println("Original LocalDateTime: "
                           + dt.toString());

        // Get a new LocalDateTime with dayOfYear 365
        System.out.println("New LocalDateTime: "
                           + dt.withDayOfYear(365));
    }
}

Output:

Original LocalDateTime: 2015-04-06T10:15:30
New LocalDateTime: 2015-12-31T10:15:30

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