DayOfWeek and Month Enums

The Date-Time API provides enums for specifying days of the week and months of the year.

DayOfWeek

The DayOfWeek enum consists of seven constants that describe the days of the week: MONDAY through SUNDAY . The integer values of the DayOfWeek constants range from 1 (Monday) through 7 (Sunday). Using the defined constants ( DayOfWeek\.FRIDAY ) makes your code more readable.

This enum also provides a number of methods, similar to the methods provided by the temporal-based classes. For example, the following code adds 3 days to "Monday" and prints the result. The output is "THURSDAY":

System.out.printf("%s%n", DayOfWeek.MONDAY.plus(3));

By using the getDisplayName(TextStyle, Locale) method, you can retrieve a string to identify the day of the week in the user's locale. The TextStyle enum enables you to specify what sort of string you want to display: FULL , NARROW (typically a single letter), or SHORT (an abbreviation). The STANDALONE TextStyle constants are used in some languages where the output is different when used as part of a date than when it is used by itself. The following example prints the three primary forms of the TextStyle for "Monday":

DayOfWeek dow = DayOfWeek.MONDAY;
Locale locale = Locale.getDefault();
System.out.println(dow.getDisplayName(TextStyle.FULL, locale));
System.out.println(dow.getDisplayName(TextStyle.NARROW, locale));
System.out.println(dow.getDisplayName(TextStyle.SHORT, locale));

This code has the following output for the en locale:

Monday
M
Mon

Month

The Month enum includes constants for the twelve months, JANUARY through DECEMBER . As with the DayOfWeek enum, the Month enum is strongly typed, and the integer value of each constant corresponds to the ISO range from 1 (January) through 12 (December). Using the defined constants ( Month\.SEPTEMBER ) makes your code more readable.

The Month enum also includes a number of methods. The following line of code uses the maxLength method to print the maximum possible number of days in the month of February. The output is "29":

System.out.printf("%d%n", Month.FEBRUARY.maxLength());

The Month enum also implements the getDisplayName(TextStyle, Locale) method to retrieve a string to identify the month in the user's locale using the specified TextStyle . If a particular TextStyle is not defined, then a string representing the numeric value of the constant is returned. The following code prints the month of August using the three primary text styles:

Month month = Month.AUGUST;
Locale locale = Locale.getDefault();
System.out.println(month.getDisplayName(TextStyle.FULL, locale));
System.out.println(month.getDisplayName(TextStyle.NARROW, locale));
System.out.println(month.getDisplayName(TextStyle.SHORT, locale));

This code has the following output for the en locale:

August
A
Aug