Java Metric Unit Conversion Library? [closed]

there is a specific JSR 275 (javax.measure) with JScience as RI (Reference Implementation). For example converting 100 Miles to kilometers is easy as:

UnitConverter toKilometers = MILE.getConverterTo(KILOMETER);
double km = toKilometers.convert(Measure.valueOf(100, MILE).doubleValue(MILE));

(note that units are all type safe a compile-time, a killer feature imho)

The reverse can be easy:

UnitConverter toMiles1 = KILOMETER.getConverterTo(MILE);

or supereasy as:

UnitConverter toMiles2 = toKilometers.inverse();

NB imports:

import javax.measure.Measure;
import javax.measure.converter.UnitConverter;
import javax.measure.quantity.Length;
import static javax.measure.unit.NonSI.*;
import static javax.measure.unit.SI.*;