protected UnitFactorMap add(Unit unit, String n, Unit base) {
    check(unit);
    check(base);
    if (unit == base) {
      throw new IllegalArgumentException("Attempt to define a unit " + unit + " in terms of itself.");
    }

    // Set the factor and its inverse if nothing already exists.
    Rational rational = new Rational(n);
    set(unit, rational, base, true);
    return this;
  }
protected UnitFactorMap add ( Unit unit , String n , Unit base ) { check ( unit ) ; check ( base ) ; if ( unit == base ) { throw new IllegalArgumentException ( "Attempt to define a unit " + unit + " in terms of itself." ) ; } Rational rational = new Rational ( n ) ; set ( unit , rational , base , true ) ; return this ; }
Set a factor to convert the unit into a given base.