Computer Science Canada

Rounding Decimal Numbers?
Author:  Delta [ Thu Jul 01, 2004 1:43 pm ]
Post subject:  Rounding Decimal Numbers?
How do you round to decimal places?
for example how do I round

8.49999999
to
8.5

Please explain. Thank you.
Author:  Paul [ Thu Jul 01, 2004 2:16 pm ]
Post subject: 
isn't it Math.round?
like
code:

System.out.println(x + " is approximately " + Math.round(x));     
Author:  Tony [ Thu Jul 01, 2004 2:53 pm ]
Post subject: 
no, Math.round would round to an integer. What you do is you multiply it by 10^number of decimal places, round, and then divide back.

such as
8.499 *10^1
84.99 ~ round
85 /10^1
8.5
Author:  Delta [ Thu Jul 01, 2004 3:28 pm ]
Post subject: 
That's the thing tony... I asked how to round...
Author:  Tony [ Thu Jul 01, 2004 3:30 pm ]
Post subject: 
i donno... you can typecast it to an (int) Laughing
Author:  wtd [ Thu Jul 01, 2004 4:13 pm ]
Post subject: 
Do you just need this for formatting text?
Author:  zylum [ Fri Jul 02, 2004 1:10 pm ]
Post subject: 
tony wrote:
no, Math.round would round to an integer. What you do is you multiply it by 10^number of decimal places, round, and then divide back.

such as
8.499 *10^1
84.99 ~ round
85 /10^1
8.5


i think tony's way is the only way to do it unless there is some weird function i havent heard of...

code:

double num = 8.4999;
num *= 10;
num = Math.round(num);
num /= 10;
// or just num = Math.round(num * 10) / 10;
System.out.println(num); // gets you 8.5
Author:  Dan [ Fri Jul 02, 2004 2:12 pm ]
Post subject: 
Thats how i do it also. Alougth u whould think there whould be a method for it some where in one of thous java APIs.
Author:  LiquidDragon [ Fri Jul 09, 2004 7:26 pm ]
Post subject: 
I always thought there was a round method. But i may be wrong Rolling Eyes
Author:  zylum [ Fri Jul 09, 2004 11:42 pm ]
Post subject: 
there is a round method but it rounds to the nearest one not the nearest tenth.
Author:  Delta [ Sat Jul 24, 2004 8:13 am ]
Post subject: 
Ok well I found some nice lil rounding methods... (I believe this was just for rounding so I could display the text)

code:
import java.text.*;

DecimalFormat decF = new DecimalFormat ("###.##");
System.out.println (decF (99999.999999));


also

code:
decF.setMinimumFractionDigits(2);

would set the format to a minimum of two decimal places

code:
decF.setMaximumFractionDigits(2);

would set the format to a maximum of two decimal places

The decimal format thing is only for text as far as I know (for outting it)...

but when it came to storing the value I usually ended up using 'long' instead of 'int' or 'double'... because long would actually round how I wanted it to... never the less... thanks for the help.... Have a nice day.

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