Constructor Example in C++


Description:

A constructor is a member function of a class which initializes objects of a class. In C++, Constructor is automatically called when object(instance of class) create. It is special member function of the class.

Example Program:

Find out the area of rectangle using constructor in C++

Source Code

#include<iostream>
using namespace std;
class Rectangle
{
private:
    int length;
    int breadth;
public :
    Rectangle() //Default Constructor
    {
        length=0;
        breadth=0;
    }
    Rectangle(int l,int b) //Parameterized Constructor
    {
        length=l;
        breadth=b ;
    }
    /*
      Rectangle(int l=0,int b=0) //Parameterized Constructor Default Arguments
        {
            length=l;
            breadth=b ;
        }
    */
    Rectangle(Rectangle &o2)
    {
        length=o2.length;
        breadth=o2.breadth;
    }
    //Constructor Overloading
    int area()
    {
        return length*breadth;
    }
    int perimeter()
    {
        return 2*(length+breadth);
    }
};
int main()
{
    Rectangle o1,o2(10,5),o3(o2);
    cout<<"\nArea : "<<o1.area();
    cout<<"\nArea : "<<o2.area();
    cout<<"\nArea : "<<o3.area();
    return 0;
}
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Output

Area : 0
Area : 50Area : 50

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