What is wrong with the following code?

class classA

{

protected:

void setX(int a); // Line 1

//postcondition: x = a; // Line 2

private: // Line 3

int x; // Line 4

};

.

.

.

int main()

{

classA aObject; // Line 5

aObject.setX(4); // Line 6

return 0; // Line 7

}