Question

I have occurred in this strange division error in a grails project (But I think grails has little to do with it, is a groovy or java question I think):

If in the groovy console I run this

float money = -1.30
float r = 0.01

println ((money/r).class.name)
println ((money/r).floatValue())
println ((money/r).toString() )

I get this output

java.lang.Double
-130.0
-129.99999813735482

The float division in groovy give me a Double, and this is correct but
why the Double toString() give me a so strange value “-129.99999813735482” and
not the correct “-130.0”?

Answer 1

As everyone says, double and float aren’t precise enough for what you’re trying to do.

One solution is to not use float as your object type, and do:

def money = -1.30
def r = 0.01

println ((money/r).class.name)
println ((money/r).floatValue())
println ((money/r).toString() )

As you can see, Groovy uses BigDecimal, which means the output is:

java.math.BigDecimal
-130.0
-130