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Calendar.HOUR_OF_DAY shows wrong timing

Posted on 2010-09-23
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Last Modified: 2012-05-10
I am trying to do some time calculation using the Calendar.HOUR_OF_DAY but it always gives the output as 11 . I tried to change the timezone in my PC to different time zone and still no difference . Where does this Java function look for the current time ? will it look in the machine in whicjh we are running the program for the current time?
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Question by:FranklinRaj22
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Expert Comment

by:HainKurt
ID: 33748041
you should use getInstance first

Calendar rightNow = Calendar.getInstance();
then use rightNow.HOUR_OF_DAY

I guess ;)
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Author Comment

by:FranklinRaj22
ID: 33748270
i assign a gregorian calendar instance before tryin to pull the hour of the day information.

Calendar calendar = new GregorianCalendar();
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Expert Comment

by:HainKurt
ID: 33748400
then use

Calendar calendar = new GregorianCalendar();
alert(calendar.HOUR_OF_DAY);

not

Calendar.HOUR_OF_DAY
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CPColin earned 500 total points
ID: 33748445
Calendar.HOUR_OF_DAY is the constant you pass to Calendar.get() to get the right value. You want something like:

calendar.get(Calendar.HOUR_OF_DAY);
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Expert Comment

by:HainKurt
ID: 33748573
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Expert Comment

by:HainKurt
ID: 33748591
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Expert Comment

by:HainKurt
ID: 33748596
sample
// create a GregorianCalendar with the Pacific Daylight time zone
 // and the current date and time
 Calendar calendar = new GregorianCalendar(pdt);
 Date trialTime = new Date();
 calendar.setTime(trialTime);

 // print out a bunch of interesting things
 System.out.println("ERA: " + calendar.get(Calendar.ERA));
 System.out.println("YEAR: " + calendar.get(Calendar.YEAR));
 System.out.println("MONTH: " + calendar.get(Calendar.MONTH));
 System.out.println("WEEK_OF_YEAR: " + calendar.get(Calendar.WEEK_OF_YEAR));
 System.out.println("WEEK_OF_MONTH: " + calendar.get(Calendar.WEEK_OF_MONTH));

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Expert Comment

by:objects
ID: 33750201
you can set the timezonme using the setTimezone() method
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Expert Comment

by:CEHJ
ID: 33752447
>>I am trying to do some time calculation using the Calendar.HOUR_OF_DAY but it always gives the output as 11

Please post your code
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Author Comment

by:FranklinRaj22
ID: 33756883
Piece of my code : Please advice.

public void run()
    {
       Thread t = Thread.currentThread();
        String name = t.getName();
        System.out.println("entered loop() - " + name);
        Calendar calendar = new GregorianCalendar();        
//int hour = Calendar.get(calendar.HOUR_OF_DAY);
        while(calendar.HOUR_OF_DAY < 20){  
         S.O.P("time is not 8 PM yet")
        }
   }
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Author Comment

by:FranklinRaj22
ID: 33756917
Thanks Guys , I did this and it wrked ....

while(calendar.get(Calendar.HOUR_OF_DAY) < 20){
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Expert Comment

by:objects
ID: 33757934
that should actually be:

public void run()
{
       Thread t = Thread.currentThread();
        String name = t.getName();
        System.out.println("entered loop() - " + name);
        while(Calendar.getInstance().get(Calendar.HOUR_OF_DAY) < 20){  
            S.O.P("time is not 8 PM yet")
        }
   }
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LVL 86

Expert Comment

by:CEHJ
ID: 33758075
You'll be eating a lot of CPU cycles like that. Use a timer with a 1 second cycle and a callback if required
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Expert Comment

by:CEHJ
ID: 33758094
>>You'll be eating a lot of CPU cycles like that.

(and unnecessary allocations)
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Author Comment

by:FranklinRaj22
ID: 33939690
let me use call back and see ..
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Expert Comment

by:mrcoffee365
ID: 37419067
This question has been classified as abandoned and is closed as part of the Cleanup Program. See the recommendation for more details.
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