How to best convert for example 2.29 -> 2.3

[Dominic Steng�rd]

Hi all math foks!
I want to find a nice and small algorithm for converting double/float values like 2.29 -> 2.3 or 8.33 -> 8.3 ...
I have a solution but I'm not satisfied with it ... have you got any ideas?
Thanks in advance!
Regards

[Marilyn de Queiroz]

How about using the Math.round() method.

[Dominic Steng�rd]

Because they return an int or long, I need a float or double.
Regards

[Dominic Steng�rd]

the solution I have figured out is this:
double i = 7;
double j = 4;
double sum = j/i * 100;
int tal = (int) sum;
double decimal = Math.round((sum - tal) * 10);
decimal = decimal/10;
sum = tal + decimal;
but it seems like alot of code for such a small operation ...

[Marilyn de Queiroz]

2.29 -> 2.3

double d = Math.round(2.29 * 10)/10.0

??

[Dominic Steng�rd]

Thanks Marilyn! That is less code than the solution I had ...

[Steve Deadsea]

I wrote a Significant Figures class that can do rounding like this. I found that when a number is to be displayed, its easiest to manipulate it in String format. You can find the class and source here:
http://ostermiller.org/utils/SignificantFigures.html