Avoiding Numerous Declarations

Question

I'm writing a class that is dependent on months and how many days each month has. At the beginning of my class, I've written:

static final int    JAN = 1;
static final int    FEB = 2;
...
static final int    DEC = 12;

It looks like a messy way of doing this, and I feel that enums would be more efficient. I need to be able to "increment" the month (where DEC + 1 = JAN), and need to be able to know have many days there are in the month (with FEB having 28).

I see two ways of doing this:

My current way, defining static final ints and using a switch statement to find the number of days, and when incrementing I always checks for whether the value would be greater than 12.
Create a set of enums, each with inputs for which month of the year it is and how many days it contains, and defining an "increment" method.

Is there a better way of doing this, or is (presumably) 2. the best way of doing this?

Don't. Simply don't do that. Please. Use the built-in classes for date-time handling. Unless you like to hurt yourself. — Tunaki
– Tunaki, Commented Feb 28, 2016 at 17:12
Look at the new Java Time API. Don't read the answers pointing to the old Calendar class... — Tunaki
– Tunaki, Commented Feb 28, 2016 at 17:19
Are there any particularly advantages/disadvantages to one or the other, or in what way do they differ in how they function? — Alex W
– Alex W, Commented Feb 28, 2016 at 17:51
Calendar is clumsy to work with and is replaced by Java Time beginning with Java 8, which is a lot easier to work with. — Tunaki
– Tunaki, Commented Feb 28, 2016 at 18:03
@AlexW The legacy date-time classes such as Date, Calendar, SimpleDateFormat, etc. are bloody awful, a train wreck of poor design, written by people who did not understand the subtleties nor complexities of date-time handling. Use only their replacement, the modern java.time classes built into Java 8 and later. — Basil Bourque
– Basil Bourque, Commented Nov 18 at 3:26

PeterJThaggard · Accepted Answer · 2016-02-28 17:16:35Z

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I recommend using java.util.Calendar for this sort of situation. It already has constants defined for virtually every date- and time-related concept that you'll ever have to use; plus, it is smart enough to know about things like February's wishy-washy length (29 days 25% of the time).

answered Feb 28, 2016 at 17:16

PeterJThaggard

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pczeus · Accepted Answer · 2016-02-28 17:16:46Z

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Java has a Class that does what you need. See the Calendar class, which also has constants for Month and Day of Week:

https://docs.oracle.com/javase/7/docs/api/java/util/Calendar.html

answered Feb 28, 2016 at 17:16

pczeus

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Basil Bourque · Accepted Answer · 2025-11-18 03:33:52Z

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java.time

I feel that enums would be more efficient

Indeed. Java 8+ comes with just such an enum: java.time.Month.

able to "increment" the month

Access any month Enum objects by its month number, 1-12 for January-December.

Month month = Month.of( 5 ) ;  // May

… (where DEC + 1 = JAN)

You can move from one month to another with plus or minus. Use positive or negative numbers. Wraps around December-January.

Month month = Month.DECEMBER.plus( 2 ) ;  // February.

how many days each month has

Interrogate each enum object. Because of Leap Year, you must specify a year.

int daysInFebruary = Month.FEBRUARY.length( 2025 ) ;

Or ask for the min/max number of days.

int min = Month.FEBRUARY.minLength() ;  // 28
int max = Month.FEBRUARY.maxLength() ;  // 29

edited Nov 18 at 3:33

answered Nov 18 at 3:22

Basil Bourque

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