code: public void setLambda0(double lambda0)
      {
          if(lambda0 < 0 || Double.isNaN(lambda0) || Double.isInfinite(lambda0))
              throw new IllegalArgumentException("Lambda0 must be non-negative, not " + lambda0);
          this.lambda0 = lambda0;
      }
docs: &lambda;<sub>0</sub> controls the L<sub>2</sub> regularization penalty.
  @param lambda0 the L<sub>2</sub> regularization penalty to use