Formatting this output to show "#.##"

[twiggy62]

How can I get the output of this program to display:

148.41 instead of 148.4131591025766

[COLOR="Blue"]public class[/COLOR] Test
{
    [COLOR="blue"]public static double[/COLOR] calculate([COLOR="blue"]final double[/COLOR] x, [COLOR="blue"]final double[/COLOR] y)
{
        [COLOR="blue"]class[/COLOR] Helper
        {
            [COLOR="blue"]double[/COLOR] doSomething()
            {
                [COLOR="blue"]return[/COLOR] Math.sqrt(x) + Math.sqrt(y);
            }
        }
        Helper h = [COLOR="Blue"]new[/COLOR] Helper();
        [COLOR="blue"]return[/COLOR] Math.exp(h.doSomething());
    }
    [COLOR="blue"]public static void[/COLOR] main(String[] args)
    {
 System.[COLOR="SeaGreen"]out[/COLOR].println(calculate(4.0, 9.0));
    }
}

[tim]

Hi Twiggy

You can achieve truncation by multiplying, casting and dividing your number as follows:

    public static void main(String[] args)
    {
        double answer = (double) ((int) (calculate(4.0, 9.0) * 100d)) / 100d;
        System.out.println(answer);
    }

Check the Math.round() method as well. ;)

Goodluck
Tim

[JosAH]

Hi Twiggy

You can achieve rounding by multiplying, casting and dividing your number

Don't do that: use a Format object to do the job; the printf( ... ) method uses those objects for its format specifiers; e.g.

System.out.printf("%.3f", 4.123456);

kind regards,

Jos

[FlyNn]

Don't do that: use a Format object to do the job; the printf( ... ) method uses those objects for its format specifiers; e.g.

Code:
System.out.printf("%.3f", 4.123456);
kind regards,

I had similar problem, am I correct to think that the output will be 4.123?

Thanks

[JosAH]

I had similar problem, am I correct to think that the output will be 4.123?

Thanks

Yep, but don't take my word for it but try it instead.

kind regards,

ps. I like your signature.

[FlyNn]

Yeah that was my next step. I should of tried it before though. My mistake.
I am glad you like the signature, thanks.

[Fubarable]

If you like printf (and I do), you can get the same result with String#format and also Formatter. The latter two are useful if you want the formatted number to appear in a non-console environment such as a Swing app.

[twiggy62]

After reviewing both proposed solutions, the real answer for me is using a combination of both.

public class Test {

    public static double calculate(final double x, final double y) {
        class Helper {

            double doSomething() {
                return Math.sqrt(x) + Math.sqrt(y);
            }
        }
        Helper h = new Helper();
        return Math.exp(h.doSomething());
    }

    public static void main(String[] args) {
        System.out.println(calculate(4.4, 9.2));
        double answer = (double) ((int) (calculate(4.4, 9.2) * 1000d)) / 1000d;
        System.out.println(answer);
        System.out.printf("%.2f", answer);
    }
}

Gives me the following results:

run:
169.1469517303579
169.146
169.15
BUILD SUCCESSFUL (total time: 1 second)

However to get these results, for the Format object, I have to multiply by 1,000 instead of 100, and if I wanted to round to nearest 100th, then I would have to multiply by 10,000, nearest 1000th multiply by 100,000, etc, etc.
My final solution would look like this:

public class Test {

    public static double calculate(final double x, final double y) {
        class Helper {

            double doSomething() {
                return Math.sqrt(x) + Math.sqrt(y);
            }
        }
        Helper h = new Helper();
        return Math.exp(h.doSomething());
    }

    public static void main(String[] args) {
        double answer = (double) ((int) (calculate(4.0, 9.0) * 1000d)) / 1000d;
        System.out.printf("%.2f", answer);
    }
}

With these results:

run:
148.41
BUILD SUCCESSFUL (total time: 1 second)

Thanks for all contributions! :)

[JosAH]

The first reply works best in my case, because I am not simply trying to format a number (using the Format object), I am also performing a calculation at the same time, so I don't know what the result is until the calculations are performed.

System.out.printf("result: %.3f", <very_complicated_calculation>);

?

kind regards,

Jos

[twiggy62]

Oh, I see where you are coming from, you are right. I was just over thinking it.

My solution would then look like this:

public class Test {

    public static double calculate(final double x, final double y) {
        class Helper {

            double doSomething() {
                return Math.sqrt(x) + Math.sqrt(y);
            }
        }
        Helper h = new Helper();
        return Math.exp(h.doSomething());
    }

    public static void main(String[] args) {
        System.out.printf("%.2", calculate(4.0, 9.0));
    }
}