code: static public double sphere_noise(double[] x) {
  
      double sum = 0.0;
  
      for (int i = 0; i < x.length; i++) {
        sum += x[i] * x[i];
      }
  
      // NOISE
      // Comment the next line to remove the noise
      sum *= (1.0 + 0.1 * Math.abs(random.nextGaussian()));
  
      return (sum);
    }
docs: Sphere function with noise