Re: Comparing floating point values in Java

Philipp wrote:
I'm aware of problems (rounding, NaN etc) when comparing floating point values in computers.

In Java, will unchanged values compare strictly true if equal?
Is it _guaranteed_ that the following code does output "true" on all JVMs?

Thanks for answers. Phil

example code:
public class Test {
public static void main(String[] args) {
float a = 1;
float b = 1;
System.out.println("a == b?: " + (a == b));
}
}

I would suggest that
any JVM where it would output false
is probably non-compliant.

Your example may be somewhat lacking
as many scalar values
and many fractions where the denominator is a cardinal exponent of 2
correspond exactly
to a floating point representation.

Personally I like to think of floating point values
as representing bounded infinite sets of real values
(or not bounded - for positive and negative infinity).


There are some that take a dim view on the liberties Sun / Gosling took in the way Java deals with IEEE754 values, eg.;
<http://www.cs.berkeley.edu/~wkahan/JAVAhurt.pdf>
.

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