Java : Get any day in a week from Calendar

Question

Using Calendar I can get the week, year and all details for the current day. How can I navigate to a particualr day in that week?

Say, calendar.get(Calendar.DAY_OF_WEEK); returns 3, which means a Tuesday. Now, I want to go to say Friday for that week or any other day in that week. How can I do that?

Thanks for your replies. I think I need to make the scenario more clear. Basically, I am trying to disable email alerts in my system during specified period. I get values like: disableStart = "FRIDAY-19:00" disableEnd = "SUNDAY-19:00"

Now, i need to verify if email should be sent at a particular time. e.g. if today = Thursday any time, send email but, if today = Saturday any time can't send as per values above.

Answer 1

If I understand correctly you can use the Calendar.set(Field, value) method.

SimpleDateFormat f = new SimpleDateFormat("dd-MM-yyyy");
Calendar c = Calendar.getInstance();
System.out.println(c.get(Calendar.DAY_OF_WEEK));
System.out.println(f.format(c.getTime()));
c.set(Calendar.DAY_OF_WEEK, Calendar.TUESDAY);
System.out.println(c.get(Calendar.DAY_OF_WEEK));
System.out.println(f.format(c.getTime()));

Produces the output

6
08-10-2010
3
05-10-2010

Answer 2

I suggest to add the appropriate amount of days like so:

Calendar cal = Calendar.getInstance(); 

// lets point it to friday
int day = cal.get(Calendar.DAY_OF_WEEK); // e.g. 3 = tuesday
cal.add(Calendar.DAY_OF_WEEK, Calendar.FRIDAY - day) // 6 - 3 = 3, 3 days added = friday.

// and back to Monday
day = cal.get(Calendar.DAY_OF_WEEK);
cal.add(Calendar.DAY_OF_WEEK, Calendar.MONDAY - day) // 2 - 6 = -4, 4 days subtracted = monday

Hope this helps.

Answer 3

cal.set(Calendar.DAY_OF_WEEK, Calendar.FRIDAY);

Answer 4

    Calendar c = Calendar.getInstance();
    Date date = new Date();
    c.setTime(date);
    System.out.println("Today:  " + c.getTime());
    c.setTime(date);
    c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
    System.out.println("MONDAY: " + c.getTime());
    c.setTime(date);
    c.set(Calendar.DAY_OF_WEEK, Calendar.TUESDAY);
    System.out.println("TUESDAY: " + c.getTime());
    c.setTime(date);
    c.set(Calendar.DAY_OF_WEEK, Calendar.WEDNESDAY);
    System.out.println("WEDNESDAY: " + c.getTime());
    c.setTime(date);
    c.set(Calendar.DAY_OF_WEEK, Calendar.THURSDAY);
    System.out.println("THURSDAY: " + c.getTime());
    c.setTime(date);
    c.set(Calendar.DAY_OF_WEEK, Calendar.FRIDAY);
    System.out.println("FRIDAY: " + c.getTime());
    c.setTime(date);
    c.set(Calendar.DAY_OF_WEEK, Calendar.SATURDAY);
    System.out.println("SATURDAY: " + c.getTime());
    c.setTime(date);
    c.set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY);
    System.out.println("SUNDAY: " + c.getTime());

Gives:

Today:  Fri Oct 08 15:45:14 CEST 2010
MONDAY: Mon Oct 04 15:45:14 CEST 2010
TUESDAY: Tue Oct 05 15:45:14 CEST 2010
WEDNESDAY: Wed Oct 06 15:45:14 CEST 2010
THURSDAY: Thu Oct 07 15:45:14 CEST 2010
FRIDAY: Fri Oct 08 15:45:14 CEST 2010
SATURDAY: Sat Oct 09 15:45:14 CEST 2010
SUNDAY: Sun Oct 10 15:45:14 CEST 2010

Which seams to mean that, at least on my system, the weeks starts on monday.

Answer 5

Thanks to Kevin and Maurice for the answers. They really gave me the start point.

I ended with this test code, in case it helps anyone.

private static Date getTimeForAnyDayInWeek(int nDay, int nHour, int nMin)
{
    Calendar c = Calendar.getInstance();
    c.setFirstDayOfWeek(Calendar.MONDAY);
    Date date = Calendar.getInstance().getTime();
    c.setTime(date);
    c.set(Calendar.DAY_OF_WEEK, nDay);
    c.set(Calendar.HOUR_OF_DAY, nHour);
    c.set(Calendar.MINUTE, nMin);
    return c.getTime();
}

public static void main(String[] args)
{
    Date start = getTimeForAnyDayInWeek(6, 19, 00);
    Date end = getTimeForAnyDayInWeek(8, 19, 00);
    Date c = new Date();

    if (start.before(c) && c.before(end))
        System.out.println("BLOCK");
    else
        System.out.println("SEND");
}

Thanks, Anubhav

Answer 6

This is a perfect example of why jodatime is so good, here is my similar code

  DateTime dt = new DateTime(); //current datetime, jodatime format
  DateTime fridayLastWeek = dt.minusWeeks(1).dayOfWeek().setCopy("Friday");
  Date convertedtorubbishdateformat = fridayLastWeek.toDate();

I used to waste so much time witht he standard java date/calendar. Then i got jodatime, you wont regret, it apparently will be used as part of standard java in the future. I didn;t bother downlaoding the jar for for ages, I wish I had done, you won't regret it.