code: public void setLambda1(double lambda1)
      {
          if(lambda1 < 0 || Double.isNaN(lambda1) || Double.isInfinite(lambda1))
              throw new IllegalArgumentException("Lambda1 must be non-negative, not " + lambda1);
          this.lambda1 = lambda1;
      }
docs: &lambda;<sub>1</sub> controls the L<sub>1</sub> regularization penalty.
  @param lambda1 the L<sub>1</sub> regularization penalty to use