CODEWITHSUNDEEP
javacalendardaysjava.util.calendar
Jerielle
Jerielle

Reputation: 7520

How to get the number of days in a specific month using Java Calendar?

I am creating a simple program that allows the user to see how many days between the months they set.

For example From January - March

I can get the current day of the month using this:

Calendar.DAY_OF_MONTH

What I want is how can I supply a value in the month?

I have this simple code:

public static void machineProblemTwo(int startMonth, int endMonth) {

        int[] month = new int[0];
        int date = 2015;

        for(int x = startMonth; x <= endMonth; x++) {
           System.out.println(x + " : " + getMaxDaysInMonth(x,date));
        }

    }

public static int getMaxDaysInMonth(int month, int year){

        Calendar cal = Calendar.getInstance();
        int days = cal.getActualMaximum(Calendar.DAY_OF_MONTH); // how can I supply the month here?

        return days;

    }

How can i do that? Can you help me with this?

Upvotes: 4

Views: 11091

Answers (3)

Aliti
Aliti

Reputation: 2095

We can do this as well:

private DateTime getNewDate(DateTime date, int dayOfMonth) {
    // first we need to make it 1st day of the month
    DateTime newDateTime = new DateTime(date.getYear(), date.getMonthOfYear(), 1, 0, 0);
    int maximumValueOfDays = newDateTime.dayOfMonth().getMaximumValue();

    // to handle the month which has less than 31 days
    if (dayOfMonth > maximumValueOfDays) {
      newDateTime = newDateTime.dayOfMonth().withMaximumValue();
    } else {
      newDateTime = newDateTime.withDayOfMonth(dayOfMonth);
    }
    return newDateTime;
  }

Upvotes: 0

Jon Skeet
Jon Skeet

Reputation: 1500525

You need to set the calendar to be in that year and month before asking for the maximum value, e.g. with

cal.set(year, month, 1);

(Or with the calendar constructor as per David's answer.)

So:

public static int getMaxDaysInMonth(int month, int year) {
    Calendar cal = Calendar.getInstance();
    // Note: 0-based months
    cal.set(year, month, 1);
    return cal.getActualMaximum(Calendar.DAY_OF_MONTH);
}

Alternatively - and preferrably - use Joda Time or Java 8:

// Java 8: 1-based months
return new LocalDate(year, month, 1).lengthOfMonth();

// Joda Time: 1-based months
return new LocalDate(year, month, 1).dayOfMonth().getMaximumValue();

(I'm sure there must be a simpler option for Joda Time, but I haven't found it yet...)

Upvotes: 8

Dawood ibn Kareem
Dawood ibn Kareem

Reputation: 79838

Use the constructor for GregorianCalendar where you pass the year, month and day. Don't forget that the months go from 0 to 11 (0 for January, 11 for December).

public static int numberOfDaysInMonth(int month, int year) {
    Calendar monthStart = new GregorianCalendar(year, month, 1);
    return monthStart.getActualMaximum(Calendar.DAY_OF_MONTH);
}

Upvotes: 6

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