find time differnce between to calender

[Amirtharaj Chinnaraj]

hi guys iam trying to find differnce between two calender instances this is my code

iam not able to get proper results

  mport java.sql.Timestamp;
import java.util.Calendar;
import java.util.Date;

public class test 
{
	
	public static void main(String as[])
	{
		Calendar one=Calendar.getInstance();
		Calendar two= Calendar.getInstance();
		 one.clear();
		 two.clear();
		
	
		one.set(Calendar.DAY_OF_MONTH, 10);
		one.set(Calendar.MONTH,6 );
		one.set(Calendar.YEAR, 2009);
		one.set(Calendar.HOUR, 8);
		one.set(Calendar.MINUTE,0 );
		one.set(Calendar.AM_PM,Calendar.AM);
		
		two.set(Calendar.DAY_OF_MONTH, 10);
		two.set(Calendar.MONTH,6 );
		two.set(Calendar.YEAR, 2009);
		two.set(Calendar.HOUR , 11);
		two.set(Calendar.MINUTE, 30);
		two.set(Calendar.AM_PM,Calendar.PM);
		
		long x= two.getTimeInMillis()- one.getTimeInMillis();
		float x1=x/1000;//sec
		
		x1=x1/60;//minu
		
		x1=x1/60;//hrs
		
		System.out.println(" x    "+x1);
		
		
	}

}
  

actually i need to 3.5 as output but i am getting 15.5

please tell me where iam wrong
looking for your replies
thanks
amir

[Campbell Ritchie]

From 8.00am 10th July to 11.30pm 10th July is 15½ hours. Look very closely at the times you are setting.

[Amirtharaj Chinnaraj]

Campbell Ritchie wrote:From 8.00am 10th July to 11.30pm 10th July is 15½ hours. Look very closely at the times you are setting.

eventhough i changed the following lines

 two.set(Calendar.HOUR , 12);
		two.set(Calendar.MINUTE, 30);   

iam getting 16.5 as output

iam thinking that from 8.00am to 12.30 pm the differnce is 4.5 hrs iam getting execess 12 hrs

that is my question

[W. Joe Smith]

Amirtharaj Chinnaraj wrote:

Campbell Ritchie wrote:From 8.00am 10th July to 11.30pm 10th July is 15½ hours. Look very closely at the times you are setting.

eventhough i changed the following lines

 two.set(Calendar.HOUR , 12);
		two.set(Calendar.MINUTE, 30);   

iam getting 16.5 as output

iam thinking that from 8.00am to 12.30 pm the differnce is 4.5 hrs iam getting execess 12 hrs

that is my question

You have the following line:

           two.set(Calendar.AM_PM,Calendar.PM);   

What does that line do?

[Amirtharaj Chinnaraj]

the line

  two.set(Calendar.AM_PM,Calendar.PM);   

is to set wether the time is for before or after Noon

W. Joe Smith wrote:

Amirtharaj Chinnaraj wrote:

Campbell Ritchie wrote:From 8.00am 10th July to 11.30pm 10th July is 15½ hours. Look very closely at the times you are setting.

eventhough i changed the following lines

 two.set(Calendar.HOUR , 12);
		two.set(Calendar.MINUTE, 30);   

iam getting 16.5 as output

iam thinking that from 8.00am to 12.30 pm the differnce is 4.5 hrs iam getting execess 12 hrs

that is my question

You have the following line:

           two.set(Calendar.AM_PM,Calendar.PM);   

What does that line do?

[Campbell Ritchie]

8.00am 10th July 10 12.00pm (midnight) 10th July is 16 hours. Add 30 minutes and you get 16½ hours. You need to check the Calendar class documentation carefully about that.

Or look elsewhere for a Calendar class anybody can actually understand

[W. Joe Smith]

Amirtharaj Chinnaraj wrote:the line

  two.set(Calendar.AM_PM,Calendar.PM);   

is to set wether the time is for before or after Noon

So, if you are setting the 11:30 to PM, and the first one is set to 8:00 AM, how many hours would be in between?

I think if you look at that you can see why you are getting 15.5 or 16.5 instead of the 3.5 or 4.5 you believe you should be getting.

[Jason Irwin]

8am is 0800; 1130pm is 2330 - the difference is 15.5hours, as your code shows. Are you sure you want the answer 3.5? Because that's not correct when you are concerned about AM and PM.

If you don't care about AM/PM, then I suggest you just either make sure both calendar instances are set to AM (or PM, doesn't matter so long as they are the same) or do basic arithmetic on the hours and minutes portions of your Calendar instance, rather than rely of milliseconds from the epoch. e.g.

int diffHours = two.get(Calendar.HOUR) - one.get(Calendar.HOUR);
float diffMInutes = (float)(two.get(Calendar.MINUTE) - one.get(Calendar.MINUTE))/60;
float diffTotal = (float)diffHours + diffMins;

Be careful not to use Calendar.HOUR_OF_DAY as that is based on the 24 hour clock and you will get the answer 15.5 again.

J.