Converting BigDecimal to long with rounding

[Janek Kowalski]

Hello Everybody,

I have problem with converting BigDecimal value to long value but with rounding applied (HALF_UP). i.e:
I have BigDecimal:

BigDecimal bd = new BigDecimal("12.78");
long l = ....;//stuff converting bd to l

After covering I'd like l to have value 13, so method longValue doesn't help.
I use following trick but I'm not happy about it, maybe there is better way to do this?

l = Math.round(bd.doubleValue());

greetings
j.k.

[Rob Spoor]

Try rounding the BigDecimal first, then calling its longValue() method:

import java.math.*;

public class Test
{
    public static void main(String[] args) throws Exception
    {
        BigDecimal bd = new BigDecimal("12.78");
        System.out.println(bd);
        long l = bd.longValue();
        System.out.println(l);
        bd = bd.round(new MathContext(bd.precision() - bd.scale(), RoundingMode.CEILING));
        System.out.println(bd);
        l = bd.longValue();
        System.out.println(l);
    }
}

The rounding takes the precision (number of digits) minus the number of decimals. This may go wrong if the rounding adds a digit (e.g. from 99.5 to 100), but initial tests show no problem.

[Till Stoschus]

Hi Janek,

if you expect that the 1st decimal place should decide rounding, then this could be a solution:

BigDecimal bd = new BigDecimal("12.78");
long l  = bd.setScale( 0, BigDecimal.ROUND_HALF_UP ).longValue();

Till

[Janek Kowalski]

Thank you very much .

Both solutions work fine.

greetings
j.k.

[Rob Spoor]

I would prefer Till's solution. It handles cases like the jump form 99.xx to 100 better.

[Janek Kowalski]

Rob Prime wrote:I would prefer Till's solution. It handles cases like the jump form 99.xx to 100 better.

I've chosen Till's solution because using this I create one object less (MathContext) but when I've changed rounding mode to HALF_UP in yours solution it worked pretty the same. (99.7 was converted to 100 properly). Perhaps I'm missing something.

greetings
j.k.