Calculate maximum number of days in given month

[Gaurav Chhabras]

Hi

I have the date JAN-02-2006 and i have to find out the maximum number of days within this month, like it has 31.
How will i calculate that.

Thanks
Regards
Gaurav

[Jesper de Jong]

You could do that like this:

- Create a Calendar object and set it to the first of the next month (for example, to 1 February 2006).
- Subtract 1 day off the calendar: cal.add(Calendar.DATE, -1);
- Get the day number of the calendar: int numberOfDaysInJanuary = cal.get(Calendar.DATE);

[Campbell Ritchie]

Do you mean you want a method which calculates number of days in the month?
Here is a totally diffrent approach:

public static final int JANUARY = . . . DECEMBER = . . ;
. . . 
public int daysInMonth(int monthNumber, boolean isLeapYear)
{
   if (monthNumber < JANUARY || monthNumber > DECEMBER)
      return 0;
   switch(monthNumber)
   {
      case FEBRUARY:
         return isLeapYear ? 29 : 28;
      case APRIL:
      case JUNE:
      case SEPTEMBER:
      case NOVEMBER:// intentional fall-through
         return 30;
      default:
         return 31;
   }// end switch
}// end method days in month

Remember that you don't need a break; statement after a return; statement. Also that the Date and Calendar classes of java.util use JANUARY = 0, DECEMBER = 11, etc.

[Stuart Ash]

Isn't a simple call to calendar.getMaximum() good enough??

[Michael Duffy]

Originally posted by Campbell Ritchie:
Do you mean you want a method which calculates number of days in the month?
Here is a totally diffrent approach:

public static final int JANUARY = . . . DECEMBER = . . ;
. . . 
public int daysInMonth(int monthNumber, boolean isLeapYear)
{
   if (monthNumber < JANUARY || monthNumber > DECEMBER)
      return 0;
   switch(monthNumber)
   {
      case FEBRUARY:
         return isLeapYear ? 29 : 28;
      case APRIL:
      case JUNE:
      case SEPTEMBER:
      case NOVEMBER:// intentional fall-through
         return 30;
      default:
         return 31;
   }// end switch
}// end method days in month

Remember that you don't need a break; statement after a return; statement. Also that the Date and Calendar classes of java.util use JANUARY = 0, DECEMBER = 11, etc.

So why do you repeat those static definitions in your class?

Too much code - why add to your maintainence burden? I like the getMaximum() call idea much better, indeed.

[Ulf Dittmer]

That's neat. The javadocs had lead me to believe that getMaximum would always return 31, and I had wondered about the use of that.

[Jim Yingst]

Indeed, getMaximum() should return 31. It's getActualMaximum() that you want here.

[Gaurav Chhabras]

Hey

Thanks a lot to you all for your instant replies.
I have found the solution for that as follows :

SimpleDateFormat df = new SimpleDateFormat("MM-dd-yyyy HH:mm:ss");
String sdate1 = "1-1-2004 00:00:00";
Date date1 = df.parse(sdate1);
Calendar cal1 = Calendar.getInstance();
cal1.setTime(date1);

maximum1 = cal1.getActualMaximum(cal1.DAY_OF_MONTH); // This will return the maximum.

If any queries then feel free to ask.

Thanks Regards
Gaurav

[Stuart Ash]

Originally posted by Jim Yingst:
Indeed, getMaximum() should return 31. It's getActualMaximum() that you want here.

Actually, I should've been clearer about this. I had been perusing this API doc with an intent to get the answer to this question sometime ago, and I wasn't sure which of the getXMaximum() methods would do the job, and hadn't tried. Glad we now have a try and its results.