Calendar setFirstDayOfWeek() Method in Java with Examples

The setFirstDayOfWeek(int day_val) method in Calendar class is used to set the first day of the week using the day_val in this Calendar.

Syntax:

public void set(int day_val)

Parameters: The method takes one parameter day_val of integer type and refers to the first day of the week.

Return Value: The method does not return any value.

Below programs illustrate the working of setFirstDayOfWeek() Method of Calendar class:
Example 1:

// Java code to illustrate
// setFirstDayOfWeek() method

import java.util.*;

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

        // Creating calendar object
        Calendar calndr = Calendar.getInstance();

        // Displaying first day of the week
        int first_day = calndr.getFirstDayOfWeek();
        System.out.println("The Current"
                           + " First day of the week: "
                           + first_day);

        // Changing the first day of week
        calndr.setFirstDayOfWeek(Calendar.THURSDAY);

        // Displaying the alternate day
        first_day = calndr.getFirstDayOfWeek();
        System.out.println("The new first"
                           + " day of the week: "
                           + first_day);
    }
}

Output:

The Current First day of the week: 1
The new first day of the week: 5

Example 2:

// Java code to illustrate
// setFirstDayOfWeek() method

import java.util.*;
public class Calendar_Demo {
    public static void main(String args[])
    {

        // Creating calendar object
        Calendar calndr
            = new GregorianCalendar(2018, 6, 10);

        // Displaying first day of the week
        int first_day = calndr.getFirstDayOfWeek();
        System.out.println("The"
                           + " First day of the week: "
                           + first_day);

        // Changing the first day of week
        calndr.setFirstDayOfWeek(Calendar.MONDAY);

        // Displaying the alternate day
        first_day = calndr.getFirstDayOfWeek();
        System.out.println("The new first"
                           + " day of the week: "
                           + first_day);
    }
}

Output:

The First day of the week: 1
The new first day of the week: 2

Reference: https://docs.oracle.com/javase/8/docs/api/java/util/Calendar.html#setFirstDayOfWeek-int-