How to get week numbers of a certain month? [close

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I just wanna ask what is the efficient way to get the week numbers of a certain month. I have a function with month number & year as arguments, the return value of the function should be a int array which contain the week numbers of the specific month.(like following...)

public int[] getWeeksOfMonth(int month, int year){
            //what's the efficient way to implement this??
}

Answer 1

I am not sure whether you want to return an array of length equal to the number of days in the month, with each value being the week number for the corresponding day, or an array of all distinct week numbers for the days in the specified month. Assuming it is the former, this should work:

public static int[] getWeeksOfMonth(int month, int year)
{
    Calendar cal = Calendar.getInstance();
    cal.set(Calendar.YEAR, year);
    cal.set(Calendar.MONTH, month);
    cal.set(Calendar.DAY_OF_MONTH, 1);

    int ndays = cal.getActualMaximum(Calendar.DAY_OF_MONTH);
    int weeks[] = new int[ndays];
    for (int i = 0; i < ndays; i++)
    {
        weeks[i] = cal.get(Calendar.WEEK_OF_YEAR);
        cal.add(Calendar.DATE, 1);
    }
    return weeks;
}

If you want an array of distinct week numbers for the days in the specified month:

public static Integer[] getWeeksOfMonth(int month, int year)
{
    Calendar cal = Calendar.getInstance();
    cal.set(Calendar.YEAR, year);
    cal.set(Calendar.MONTH, month);
    cal.set(Calendar.DAY_OF_MONTH, 1);

    Set<Integer> weeks = new HashSet<Integer>();
    int ndays = cal.getActualMaximum(Calendar.DAY_OF_MONTH);
    for (int i = 0; i < ndays; i++)
    {
        weeks.add(cal.get(Calendar.WEEK_OF_YEAR));
        cal.add(Calendar.DATE, 1);
    }

    return weeks.toArray(new Integer[0]);
}

(Note this last example returns an array of Integer objects, but it is trivial to modify it to return an array of int instead)

Answer 2

Calendar cal = Calendar.getInstance();

int maxWeeknumber = cal.getActualMaximum(Calendar.WEEK_OF_MONTH);

Answer 3

1. Create Calendar instances for the first and last day of the month.
2. then on each instance invoke the get(Calendar.WEEK_OF_YEAR)
3. Step [2] will return starting and ending index for the weeks

Answer 4

The WEEK_OF_YEAR attribute of the Calendar class can be usefull for you.

Create a new date that will be the first day of the given month. Get the week of the year for this day, let say you got start value.

Create a new date that will be the last day of the given month. Get the week of the year for this day, so now you got end value.

Finally, create a simple int[] that will contains values from start to end.

Answer 5

I think, that this is much simpler way:

Calendar now = Calendar.getInstance();

System.out.println("Current week of month is : " +
            now.get(Calendar.WEEK_OF_MONTH));