code: public Matrix getIplus() {
          Matrix Iplus = new Matrix(size, size);
          int i, j;
          for (i = 0; i < size; i++)
              for (j = 0; j < size; j++)
                  Iplus.matrix[i][j] = 0d;
          for (i = 1; i < size; i++)
              Iplus.matrix[i - 1][i] = Math.sqrt(J * J + J - (J - i + 1) * (J - i + 1) + (J - i + 1));
          return Iplus;
      }
docs: Calculates the I+ operator