TemporalAdjusters firstInMonth() method in Java with Examples

The firstInMonth(DayOfWeek) method of a TemporalAdjusters class is used to return a TemporalAdjuster object which can be used to get a new Date object which is the first date of the same month with the same matching DayOfWeek as passed as a parameter from any Date object on which this TemporalAdjuster is applied. Syntax:

public static TemporalAdjuster
       firstInMonth(DayOfWeek dayOfWeek)

Parameters: This method accepts dayOfWeek which can be used to get a new Date object which is the first date of the same month with the same matching DayOfWeek. Return value: This method returns the first in month adjuster, not null. Below programs illustrate the TemporalAdjusters.firstInMonth() method: Program 1:

Java

// Java program to demonstrate
// TemporalAdjusters.firstInMonth()

import java.time.*;
import java.time.temporal.*;

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

        // get TemporalAdjuster with
        // the first in month adjuster
        TemporalAdjuster temporalAdjuster
            = TemporalAdjusters.firstInMonth(
                DayOfWeek.SUNDAY);

        // using adjuster for local date time
        LocalDate localDate
            = LocalDate.of(2023, 10, 11);
        LocalDate firstInMonth
            = localDate.with(temporalAdjuster);

        // print
        System.out.println(
            "First date in month having"
            + " sunday for localdate "
            + localDate + " is: "
            + firstInMonth);
    }
}

Output:

First date in month having sunday for localdate 2023-10-11 is: 2023-10-01

Program 2:

Java

// Java program to demonstrate
// TemporalAdjusters.firstInMonth() method

import java.time.*;
import java.time.temporal.*;

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

        // get TemporalAdjuster with
        // the first in month adjuster
        TemporalAdjuster temporalAdjuster
            = TemporalAdjusters.firstInMonth(
                DayOfWeek.TUESDAY);

        // using adjuster for local date-time
        LocalDate localDate
            = LocalDate.of(2023, 10, 11);
        LocalDate firstInMonth
            = localDate.with(temporalAdjuster);

        // print
        System.out.println(
            "First date in a month having"
            + " TUESDAY for localdate "
            + localDate + " is: "
            + firstInMonth);
    }
}

Output:

First date in a month having TUESDAY for localdate 2023-10-11 is: 2023-10-03

References: https://docs.oracle.com/javase/10/docs/api/java/time/temporal/TemporalAdjusters.html#firstInMonth(java.time.DayOfWeek)