BigDecimal representation problem

[gehel]

Worst case, you can always extract the needed code from commons-math and adapt it for BigDecimal. It doesnt seem to be too hard to understand and should not be too hard to adapt.

[dr_pompeii]

Hello gehel

about of formating string x/y thats done

the problem is for 14/6 = 2.333.....
or
14.00/6.00
see that this constructor recieve the number, i think already divided
for my bad luck 2.34

public Fraction(double value,
                double epsilon,
                int maxIterations)
         throws FractionConversionException

i need a method that recieve 2 bigdecimals or 2 doubles to resolve
the problem about 14 and 6

                BigDecimal a = new BigDecimal("14.1515");
		Double da = new Double(a.toString());
		System.out.println("a: "+a+" da: "+da);
		BigDecimal b = new BigDecimal("6.18");
		Double db = b.doubleValue();		
		System.out.println("b: "+b+" db: "+db);

show

a: 14.1515 da: 14.1515
b: 6.18 db: 6.18
c: 2.2899 dc: 2.2899

so i can play with BigDecimals or doubles

thanks in advanced

[dr_pompeii]

just after to try my last option like playing

               BigDecimal a = new BigDecimal("14.00");
		Double da = new Double(a.toString());
		System.out.println("a: "+a+" da: "+da);
		BigDecimal b = new BigDecimal("6.00");
		Double db = b.doubleValue();		
		System.out.println("b: "+b+" db: "+db);

		BigDecimal c = a.divide(b,3); //<--------------- 3 instead of 2
		Double dc = c.doubleValue();
		System.out.println("c: "+c+" dc: "+dc);

show

a: 14.00 da: 14.0
b: 6.00 db: 6.0
c: 2.33 dc: 2.33  <---------- the desired value

so why 14/6 = 2.33333333....
for

BigDecimal c = a.divide(b,2);

is 2.34
and for

BigDecimal c = a.divide(b,3);

2.33

it should be the same?

regards

[Andreas Senft]

The int argument of divide() is the rounding-mode which is used to round to the given scale (in your case the scale is 2).
Rounding mode 2 stands for ROUND_CEILING and 3 for ROUND_FLOOR. So that makes the difference.

Try out this:

BigDecimal bd = new BigDecimal(2.333d);
System.out.println(bd.scale(2, RoundingMode.CEILING));
System.out.println(bd.scale(2, RoundingMode.FLOOR));

It yields 2.34 and 2.33.

Regards,
Andreas

[dr_pompeii]

Hi Andreas

BigDecimal bd = new BigDecimal(2.333d);
System.out.println(bd.setScale(2, RoundingMode.CEILING));
System.out.println(bd.setScale(2, RoundingMode.FLOOR));

show

2.34
2.33

thats right

but in the sun forums, i recieved the same suggestion,

about RoundingMode.CEILING

in
http://java.sun.com/j2se/1.5.0/docs/...e.html#CEILING

CEILING
 
public static final RoundingMode CEILING
 
    Rounding mode to round towards positive infinity. If the result is positive, behaves as for RoundingMode.UP; if negative, behaves as for RoundingMode.DOWN. Note that this rounding mode never decreases the calculated value.
 
    Example:
    Input Number 	Input rounded to one digit
    with CEILING rounding
    5.5 	6
    2.5 	3
    1.6 	2
    1.1 	2
    1.0 	1
    -1.0 	-1
    -1.1 	-1
    -1.6 	-1
    -2.5 	-2
    -5.5 	-5

according to this (no tested yet) 0.33..... would become 1

ant i can remember that this behaviour happens, thats the reason i avoid it, coz all my control of historial of prices gone wrong with this behaviour

now i am really wondered and confused why in your case it works

regards

[foridea]

The int argument of divide() is the rounding-mode which is used to round to the given scale (in your case the scale is 2).
Rounding mode 2 stands for ROUND_CEILING and 3 for ROUND_FLOOR. So that makes the difference.

Try out this:

BigDecimal bd = new BigDecimal(2.333d);
System.out.println(bd.scale(2, RoundingMode.CEILING));
System.out.println(bd.scale(2, RoundingMode.FLOOR));

It yields 2.34 and 2.33.

Regards,
Andreas

thanks the knowledge became useful