WeekFields of() method in Java with Examples

The of() method of WeekFields class helps us to obtain an instance of WeekFields.

There are two types of of() methods based on parameters passed to it.

1. of(DayOfWeek firstDayOfWeek, int minimalDaysInFirstWeek): This method helps us to an instance of WeekFields from the first day-of-week and minimal days.WeekFields instances are singletons; for each unique combination of firstDayOfWeek and minimalDaysInFirstWeek the same instance will be returned.

   Syntax:

   public static WeekFields of(DayOfWeek firstDayOfWeek, 
                             int minimalDaysInFirstWeek)
   

   Parameters: This method accepts two parameters:

   • firstDayOfWeek which is the first day of the week. It should not be null
   • minimalDaysInFirstWeek which is the minimal number of days in the first week, from 1 to 7.

   Return value: This method returns the week-definition, not null.

   Exception: This method throws IllegalArgumentException if the minimal day’s value is less than one or greater than 7.

   Below program illustrate the WeekFields.of(DayOfWeek firstDayOfWeek, int minimalDaysInFirstWeek) method:
   Program 1:

   
   

   
   
   

   // Java program to demonstrate // WeekFields.of(DayOfWeek, int) method    import java.time.DayOfWeek; import java.time.temporal.WeekFields;    public class GFG {     public static void main(String[] args)     {            // create WeekFields         WeekFields weekFields             = WeekFields.of(DayOfWeek.MONDAY, 1);            // print results         System.out.println(weekFields);     } }
   Output:

   WeekFields[MONDAY, 1]
   

2. of(Locale locale): This method help us to get an instance of WeekFields appropriate for a locale.
   Syntax:

   public static WeekFields of(Locale locale)
   

   Parameters: This method accepts locale as a parameter which is the locale to use. It should not be null.

   Return value: This method returns the week-definition, not null.

   Below program illustrate the WeekFields.of(long min, long maxSmallest, long maxLargest) method:
   Program 2:

   
   

   
   
   

   // Java program to demonstrate // of(Locale locale) method    import java.time.temporal.WeekFields; import java.util.Locale;    public class GFG {     public static void main(String[] args)     {            Locale locale = new Locale("EN", "US");            // create WeekFields         WeekFields weekFields = WeekFields.of(locale);            // print results         System.out.println(weekFields);     } }
   Output:

   WeekFields[SUNDAY, 1]
   

References: https://docs.oracle.com/javase/10/docs/api/java/time/temporal/WeekFields.html