code: public void setScale(double scale)
      {
          if(scale <= 0 || Double.isNaN(scale) || Double.isInfinite(scale))
              throw new ArithmeticException("Scale must be a positive value, not " + scale);
          this.scale = scale;
          this.logScale = log(scale);
      }
docs: Sets the scale of the Levy distribution
  @param scale the new scale value, must be positive