Hi,
You are right this is not relevent to servlets !!! :-( (bad boy, sit in the
corner and face the wall!)
However it is the wonders of floating point arithmatic for you This is because .1
cannot be represented exactly as a double (or, for that matter, as a binary
fraction of any finite length).
you could do this however,
import java.math.BigDecimal;
public class Mathtest {
static public void main(String[] args){
double a = 0.7;
double b = 0.6;
BigDecimal c = new BigDecimal(a).subtract(new BigDecimal(b));
BigDecimal d = c.setScale(2, BigDecimal.ROUND_HALF_UP);
System.out.println("a=" + a + " b=" + b + " d=" + d );
}
}
Karl
Tsao Su Jen wrote:
> Sorry for posting this off-topic question here, but since people in this list
> have most probably coded extensively with Java, I'm hoping somebody can provide
> some insights. In my java program, an expression like the following evaluates
> to false:
> (0.7 - 0.6 == 0.1)
>
> The following code snipplet:
> double a = 0.7;
> double b = 0.6;
> double c = a - b;
> System.out.println("a=" + a + " b=" + b + " c=" + c);
> gives the result:
> a=0.7 b=0.6 c=0.09999999999999998
>
> Why is the result of the above operation not exact? If this is the expected
> behaviour, what would be a good way to handle such numeric operations and
> comparisons, e.g. when we're doing data validation?
>
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