When you convert between 2 entities, you usually do it via the UnitConverter. How should I find out what the conversion factor is? For example:
public static final Unit<Length> KILOMETRE = METER.times(1000);
public static final Unit<Length> CENTIMETRE = METRE.divide(100);
I would like to get the conversion factor programmatically from the converter interfaces (i.e. 1000 b/w KILOMETRE and METER or 1/100 in case of CENTIMETER to METRE)
I am not sure how to fetch this information from the UnitConverter interface.
EDIT1
protected double getConvFactor(Unit<Length> from, Unit<Length> to) {
double factor = -1;
UnitConverter unitConverter = from.getConverterTo(to);
if (unitConverter instanceof MultiplyConverter) {
MultiplyConverter multiplyConverter = (MultiplyConverter) unitConverter;
factor = multiplyConverter.getFactor();
} else if (unitConverter instanceof AddConverter) {
AddConverter addConverter = (AddConverter) unitConverter;
factor = addConverter.getOffset();
} else if (unitConverter instanceof RationalConverter) {
RationalConverter rationalConverter = (RationalConverter) unitConverter;
double divisor = rationalConverter.getDivisor().doubleValue();
double dividend = rationalConverter.getDividend().doubleValue();
factor = divisor;
}
}
Edit after further code posted by OP:
UnitConverter
is an abstract class, so one must derive from it to create a converter for the specific units you have in mind.If you're already using a class derived from
UnitConverter
, you'll have to check it's interface to see if the designer of that class was good enough to expose a method that returns the multiplication factor.Looking at some of the jscience classes derived from
UnitConverter
:MultiplyConverter
has agetFactor()
method which returns the factor being used in the conversion.AddConverter
has agetOffset()
method which returns the offset the converter adds in the conversion.RationalConverter
, if I understand it correctly, converts by multiplying the value being converted by the quotient of two numbers - the dividend and the divisor. The class has methods,getDividend()
andgetDivisor()
for returning the dividend and the divisor, so you could perform the division yourself to approximate the quotient.So I think your code (below) is in error. The factor is NOT the divisor, as you have here - it's the quotient.