toString-ing floats and doubles
Archie Cobbs
archie at whistle.com
Wed Jun 28 10:34:25 PDT 2000
Stuart Ballard writes:
> Is the conversion from a float or double to a String in Java supposed to
> be 100% deterministic and give identical results from one implementation
> to another?
Yes... emphasis on "supposed to"..
> I notice that System.out.println(Math.E) gives a slightly different
> result under Kaffe from JDK1.1, and since Math.E is a compiletime
> constant, I know I'm printing the value that my code was *compiled*
> against, so the problem isn't just that Kaffe defines E slightly
> differently than JDK. A similar result occurs with Math.PI, or any other
> float/double constant.
>
> Trivial and obvious sample code:
> public class TestE {
> public static void main(String[] args) {
> System.out.println(Math.E);
> }
> }
>
> Compile it (against either JDK or Kaffe) and then run the same bytecode
> against both Kaffe and JDK. Kaffe's output:
> 2.7182818284590451
>
> JDK1.1 output:
> 2.718281828459045
This is a known problem.. from FAQ.Known-Bugs..
* The conversion of floats or doubles to strings does not completely
conform to Sun's spec. For example, Double.toString() will display
the double 0x400B333333333333 as "3.3999999999999999" instead of "3.4".
If you would like to work on improving this code that would be
warmly encouraged.
-Archie
___________________________________________________________________________
Archie Cobbs * Whistle Communications, Inc. * http://www.whistle.com
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