udunits/src/main/java/ucar/units/SI.java
public static synchronized SI instance() throws UnitSystemException {
    if (si == null) {
      try {
        si = new SI();
      } catch (final UnitException e) {
        throw new UnitSystemException("Couldn't initialize class SI", e);
      }
    }
    return si;
  }
public static synchronized SI instance() throws UnitSystemException {
    if (si == null) {
      try {
        si = new SI();
      } catch (final UnitException e) {
        throw new UnitSystemException("Couldn't initialize class SI", e);
      }
    }
    return si;
  }
Returns an instance of the SI system of units.

@return An instance of the SI system of units.
@throws UnitSystemException Couldn't create an instance of the SI system of units.