Using Math.round to round to one decimal place?

Question

I have these two variables

double num = 540.512
double sum = 1978.8

Then I did this expression

double total = Math.round((         


        

Answer 1

The Math.round method returns a long (or an int if you pass in a float), and Java's integer division is the culprit. Cast it back to a double, or use a double literal when dividing by 10. Either:

double total = (double) Math.round((num / sum * 100) * 10) / 10;

or

double total = Math.round((num / sum * 100) * 10) / 10.0;

Then you should get

27.3