Print Out an Array of Objects C++

You need to overload the <<operator for the Circle class as you need it (here you need to display the radius of the Circle object) As a parameter, you give it a Circle object.

In the class, I added the line :

friend std::ostream& operator<< (std::ostream &out, const Circle &matrix);

And outside the class its definition like this:

std::ostream& operator<< (std::ostream& out, const Circle& matrix)
{
    out << "Circle radius " << matrix.radius<<std::endl;
}

Then in the main function, your loop shall be modified to only give a Circle object like this:

for (int index = 0; index < size; index++)
{
      //cout << arr[index].Circle();  //Error: Invalid use of Circle::Circle
      cout << arr[index]; // no error as you defined operator <<for your Circle class
}

Here is you complete code modified

#include <iostream>

using namespace std;

class Circle
{
    private:
        double radius;
    public:
        Circle() //Constructor
        {   radius = 0; }

        Circle(double); //Parameterized Constructor

        void setRadius(double);

        double getRadius() const
        { return radius; }

        double getArea() const
        { return 3.14 * radius * radius; }

        friend std::ostream& operator<< (std::ostream &out, const Circle &matrix);

};

std::ostream& operator<< (std::ostream& out, const Circle& matrix)
{
    out << "Circle radius " << matrix.radius<<std::endl;
}

Circle::Circle(double r)
{
    radius = r;
}

void Circle::setRadius(double r)
{
    radius = r;
}

int main()
{
    int size = 3;  //Set size of array of objects
    Circle arr[size] = { Circle(1.2), Circle(2.2), Circle(5.5) }; //Array of Objects

    for (int index = 0; index < size; index++)
    {
      //cout << arr[index].Circle();  //Error: Invalid use of Circle::Circle
      cout << arr[index]; // no error as you defined operator <<for your Circle class    
   }

    Circle b(2.8);                  //Instance of class
    cout << b.getRadius();          //Prints out the radius of object

    Circle c;                       //Another instance
    cout << endl << c.getRadius(); //Another radius

    double r;                     //Variable to store the radius based on user input
    cout << "\nEnter a radius: ";
    cin >> r;
    c.setRadius(r);             //Pass user input into radius member function
    cout << c.getRadius();      //Print new radius of object c
    cout << endl << c.getArea(); //Prints area of object c.


    return 0;

}

The output is:

Circle radius 1.2
Circle radius 2.2
Circle radius 5.5
2.8
0
Enter a radius: 5
5
78.5