Java Precission rounding.

Tru_Messiah · 05-13-2004, 07:01 AM

I'm writing a program that involves multiplying two numbers of double precision, but I need to display the numbers rounded to two decimal places without losing precion. How do I do this???

Thakns in advance...

Tru_Messiah · 05-13-2004, 07:31 AM

Meh, so far I have managed to reduce the double to only two numbers but doing the following...

temp = (int) (cost * 100);
cost = (double) temp / 100;

(cost is the number I want rounding)

However this just reduces the number form say 234.567 to 234.56 and it doesn't round it at all. How would I go about actually rounding it to 234.57.

thanks...

Looking_Lost · 05-13-2004, 08:35 AM

Something like this will do it....

Code:

import java.math.BigDecimal;

...blah...blah...

double myDouble=234.567544;
           
BigDecimal bd=new BigDecimal(myDouble).setScale(2,BigDecimal.ROUND_HALF_UP);
         
myDouble=bd.doubleValue();

take a look at the BigDecimal class to tailor it (although I'll bet there's more than one way

)

Tru_Messiah · 05-13-2004, 09:03 AM

Thank you, that seems to work....

eric.r.turner · 05-14-2004, 11:23 PM

I noticed that your example is dealing with dollar amounts. If you want a nice, readable currency representation that is easy to format for different countries, you can use the NumberFormat class.

Code:

import java.text.NumberFormat;
import java.util.Locale;

public class NumberFormatExample {

    public static void main( String[] args ) {

        double cost = 123.456;
        NumberFormat currency = NumberFormat.getCurrencyInstance(Locale.US);
        System.out.println( currency.format( cost ) );
    }

}

There are many other ways of formatting the output using the NumberFormat class. Check it out in the API.