Calendar Object - updateTime()

[Brian Ata]

Hi Guys,

For doing Time Zone calculations, I was toying with the below code sniplet:

   

            TimeZone timeZone1 = TimeZone.getTimeZone("Europe/Istanbul");

            Calendar calendar = new GregorianCalendar();

            cal.setTime(new Date());

            calendar.set(Calendar.HOUR_OF_DAY, 10);
            calendar.set(Calendar.MINUTE, 16);
            calendar.set(Calendar.SECOND, 31);
            calendar.set(Calendar.MILLISECOND, 0);

            // Without this line , time zone calculations do not work
            //long timeLocal = calendar.getTimeInMillis();

            calendar.setTimeZone(timeZone1);

            System.out.println("Hour     = " + calendar.get(Calendar.HOUR_OF_DAY));
            System.out.println("Minute     = " + calendar.get(Calendar.MINUTE));
            System.out.println("Second     = " + calendar.get(Calendar.SECOND));
      
            System.out.println("DAY     = " + calendar.get(Calendar.DAY_OF_MONTH));
            System.out.println("MONTH     = " + calendar.get(Calendar.MONTH) );
            System.out.println("YEAR     = " + calendar.get(Calendar.YEAR));

 

There is a seven hours different between Istanbul, and my developer machine, which is in America/New_York
Time Zone ID.

From the above sniplet, the results are:

Hour = 10
Minute = 16
Second = 31
DAY = 20
MONTH = 9
YEAR = 2010
BUILD SUCCESSFUL (total time: 0 seconds)

which in turn means , the time zone calculation isn't done, the values outputted belongs to local zone,so I jumped into calendar's source code and realized
that when I set day, month, etc.. the following block of code executes:

   

 public void set(int field, int value)
    {
	if (isLenient() && areFieldsSet && !areAllFieldsSet) {
	    computeFields();
	}
	internalSet(field, value);
        isTimeSet = false;
	areFieldsSet = false;
        isSet[field] = true;
        stamp[field] = nextStamp++;
	if (nextStamp == Integer.MAX_VALUE) {
	    adjustStamp();
	}
    }

 

Here there is isTimeSet variable set to false, which is logical assuming that I am pushing new data to object,
changing its state. So since the state is changed, I need to force update somehow with a member function,
but I couldn't see one > again I was fooling around the source code, and I realized when I call getTimeInMillis()
function of the calendar, it forces an internal update, here is function itself:

   

 public long getTimeInMillis() {
        if (!isTimeSet) {
	    updateTime();
	}
        return time;
    }

 

So if I do not uncomment the part below from the code I posted in the beginning of this post, the algorithm never works correctly,
since it seems that the time information is never updated internally. After uncommenting the below section, i can get correct values
for the calculated time, date difference.

    

           // Without this line , time zone calculations do not work
            //long timeLocal = calendar.getTimeInMillis();

Outputs (7 hrs difference):

Hour = 17
Minute = 16
Second = 31
DAY = 20
MONTH = 9
YEAR = 2010
BUILD SUCCESSFUL (total time: 0 seconds)


So after this long, boring, maybe based on wrong assumptions? post, my question is how you guys do it?
It shouldn't be like this I hope? I should be doing smtg wrong.

Thanks all!