Constructor
name is same name as that of class name
It
does not have any return type
It
can be overloaded
It
is called when object is created.
By
default default constructor is called when object is created
It
is used to initialize the instance variable of an object
Types:
There
are three types of constructor in java
1)
Default constructor (No arguments)
2)
Parameterized constructor (Having argument)
3)
Copy constructor
1) Default constructor (No
arguments)
A constructor which has no
argument is known as default constructor. It is invoked at the time of creating
object. By
default default constructor is
called when object is created
Example:
#include
<iostream.h>
#include<conio.h>
class A
{
public:
A()
{
cout<<"Hi, Welcome to
LearningPoint92"<<endl;
}
};
void main()
{
clrscr();
A a1;
getch();
}
Output:
Hi, Welcome to
LearningPoint92
2)Parameterized Constructor
A constructor which has parameters is called as Parameterized Constructor.
2)Parameterized Constructor
A constructor which has parameters is called as Parameterized Constructor.
Example:
#include
<iostream.h>
#include<conio.h>
class Add
{
public:
Add (int a,int b)
{
cout<<"sum
is:"<<a+b<<endl;
}
};
void main()
{
clrscr();
Add a1(55,45);
getch();
}
Output:
Sum is :100
3)Copy constructor
Copy constructor takes an object as argument, and is used to copy values of data members of one object into other object
Copy constructor takes an object as argument, and is used to copy values of data members of one object into other object
Copy Constructor is a type of
constructor which is used to create a copy of an already existing object of a
class type.
Syntax:
class_name(const class_name
& obj_name);
Example:
A (const A &
s1)
Example:
#include<iostream.h>
#include<conio.h>
class A
{
public:
int a, b; // data
members
public:
A(int x, int y)
{
a=x;
b=y;
}
// Copy constructor
A (const A &
s1)
{
a = s1.a;
b = s1.b;
}
void display()
{
cout<<a<<"
"<<b<<endl;
}
};
void main()
{
clrscr();
A obj1(30, 45); //
Default constructor
A obj2 = obj1; //
Copy constructor
cout<<"Original
constructor Value: ";
obj1.display();
cout<<"Copied
constructor value: ";
obj2.display();
getch();
}
Output:
Original constructor
Value: 30 45
Copied constructor
value: 30 45
Constructor (constructor is
used to initialize instance variable of an object)
Example:
#include<iostream.h>
#include<conio.h>
class A{
public:
int x,y;
A( int a,int b)
{
x=a;
y=b;
cout<<"sum is:"<<x+y<<endl;
}
};
void main()
{
clrscr();
A a1(55,45);
getch();
}
Output:
Sum is:100
Constructor (Using method)
#include<iostream.h>
#include<conio.h>
class A{
public:
int
x,y;
A(
int a,int b)
{
x=a;
y=b;
}
void
show()
{
cout<<"sum is:"<<x+y<<endl;
}
};
void
main()
{
clrscr();
A a1(55,45);
a1.show();
getch();
}
Output:
Sum is:100
Constructor(Constructor can
be overloaded)
#include<iostream.h>
#include<conio.h>
class A
{
public:
int
x,y;
A(int
a) //constructor having one parameter
{
x=a;
cout<<" Value is: <<x<<endl;
}
A( int a,int b) //
{
x=a;
y=b;
cout<<"sum
is:"<<x+y<<endl;
}
};
void main()
{
clrscr();
A a1(56);
A a2(55,45);
getch();
}
Output:
Value is:56
Sum is:100
Constructor (using this
keyword)
#include<iostream.h>
#include<conio.h>
class
A
{
public:
int
x,y;
A(
int x,int y)
{
this->x=x;
this-> y=y;
}
void show()
{
cout<<"sum
is:"<<x+y<<endl;
}
};
void main()
{
clrscr();
A
a2 (55,45);
a2.show();
getch();
}
Output:
sum
is:100
Constructor (Taking input
from user)
#include<iostream.h>
#include<conio.h>
class A{
public:
int x,y;
A( int a,int b)
{
x=a;
y=b;
cout<<"sum
is:"<<x+y<<endl;
}
};
void main()
{
int a,b;
clrscr();
cout<<"Enter
two number"<<endl;
cin>>a>>b;
A a1(a,b);
getch();
}
Output:
Enter two number
55
45
sum
is:100
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