public Matrix getCoMatrix() throws MatrixException {
        if (!isSquared()) {
            return null;
        }
        Matrix m = new Matrix(getNumRows(), getNumColumns());
        for (int i = 0; i < getNumRows(); i++) {
            for (int j = 0; j < getNumColumns(); j++) {
                Matrix subMatrix = this.getSubmatrix(i,j);
                m.setElement(i, j, changeSign(i) * changeSign(j) * subMatrix.getDeterminant());
            }
        }

        return m;
    }

public Matrix getSubmatrix(int line, int col) throws MatrixException {
        try {
            Matrix m = new Matrix(getNumColumns() - 1, getNumColumns() - 1);

            int r = -1;

            for (int i = 0; i < getNumRows(); i++) {
                if (i == line)
                    continue;

                r++;
                int c = -1;

                for (int j = 0; j < getNumColumns(); j++) {
                    if (j == col)
                        continue;

                    m.setElement(r, ++c, getElement(i, j));
                }
            }

            return m;
        } catch (IndexOutOfBoundsException e) {
            throw new MatrixException("Invalid line or column parameter");
        }
    }