code: public DenseMatrix nullspace() {
          if (!full) {
              throw new IllegalStateException("This is not a FULL singular value decomposition.");
          }
  
          int nn = 0;
          DenseMatrix nullsp = Matrix.zeros(n, nullity());
          for (int j = 0; j < n; j++) {
              if (s[j] <= tol) {
                  for (int jj = 0; jj < n; jj++) {
                      nullsp.set(jj, nn, V.get(jj, j));
                  }
                  nn++;
              }
          }
          return nullsp;
      }
docs: Returns a matrix of which columns give an orthonormal basis for the null space.