public abstract class GenericMatrix<E extends Number> {
  /** Abstract method for adding two elements of the matrices */
  protected abstract E add(E o1, E o2);

  /** Abstract method for multiplying two elements of the matrices */
  protected abstract E multiply(E o1, E o2);

  /** Abstract method for defining zero for the matrix element */
  protected abstract E zero();

  /** Add two matrices */
  public E[][] addMatrix(E[][] matrix1, E[][] matrix2) {
    // Check bounds of the two matrices
    if ((matrix1.length != matrix2.length) ||
        (matrix1[0].length != matrix2[0].length)) {
      throw new RuntimeException(
        "The matrices do not have the same size");
    }

    E[][] result =
      (E[][])new Number[matrix1.length][matrix1[0].length];

    // Perform addition
    for (int i = 0; i < result.length; i++)
      for (int j = 0; j < result[i].length; j++) {
        result[i][j] = add(matrix1[i][j], matrix2[i][j]);
      }

    return result;
  }

  /** Multiply two matrices */
  public E[][] multiplyMatrix(E[][] matrix1, E[][] matrix2) {
    // Check bounds
    if (matrix1[0].length != matrix2.length) {
      throw new RuntimeException(
        "The matrices do not have compatible size");
    }

    // Create result matrix
    E[][] result =
      (E[][])new Number[matrix1.length][matrix2[0].length];

    // Perform multiplication of two matrices
    for (int i = 0; i < result.length; i++) {
      for (int j = 0; j < result[0].length; j++) {
        result[i][j] = zero();

        for (int k = 0; k < matrix1[0].length; k++) {
          result[i][j] = add(result[i][j],
            multiply(matrix1[i][k], matrix2[k][j]));
        }
      }
    }

    return result;
  }

  /** Print matrices, the operator, and their operation result */
  public static void printResult(
      Number[][] m1, Number[][] m2, Number[][] m3, char op) {
    for (int i = 0; i < m1.length; i++) {
      for (int j = 0; j < m1[0].length; j++)
        System.out.print(" " + m1[i][j]);

      if (i == m1.length / 2)
        System.out.print("  " + op + "  ");
      else
        System.out.print("     ");

      for (int j = 0; j < m2.length; j++)
        System.out.print(" " + m2[i][j]);

      if (i == m1.length / 2)
        System.out.print("  =  ");
      else
        System.out.print("     ");

      for (int j = 0; j < m3.length; j++)
        System.out.print(m3[i][j] + " ");

      System.out.println();
    }
  }
}