udunits/src/main/java/ucar/units/StandardUnitDB.java
private void au(final String name, final String definition)
          throws UnitExistsException, NoSuchUnitException,
          UnitParseException, SpecificationException, UnitDBException,
          PrefixDBException, OperationException, NameException,
          UnitSystemException {
    au(name, definition, null);
  }
private void au(final String name, final String definition)
          throws UnitExistsException, NoSuchUnitException,
          UnitParseException, SpecificationException, UnitDBException,
          PrefixDBException, OperationException, NameException,
          UnitSystemException {
    au(name, definition, null);
  }
Adds a derived unit to the database.

@param name       The name of the unit.
@param definition The definition for the unit.
@throws UnitExistsException    Attempt to redefine an existing unit.
@throws NameException          Bad unit name.
@throws UnitParseException     A string specification couldn't be parsed.
@throws SpecificationException Bad string specification.
@throws UnitDBException        Problem with the unit database.
@throws PrefixDBException      Problem with the prefix database.
@throws NameException          Bad unit name.
@throws OperationException     Improper unit operation.
@throws UnitSystemException    Problem with UnitSystem.