How many number of Objects created

[Ankur Mahajan]

Hi All

I have small doubt regarding, number of objects created in case when a sub class is instantiated.

e.g.

    
class A
{
 
}
 
class B extends A{
 
public static void main(String args[]){
   
  B b = new B(); // object of subclass is created
 
}
 
}
 

Now the question is, when constructor of class B is called it will call the constructor of Class A and then from A contructor of Object class is created.

So a total of 3 objects should be created in heap.
Please some validate the same.

If this is true then how it is done in case of abstract class as its objects cannot be created.


TIA

[Jolly Tiwari]

Hi! Ankur,

This is not the way you are percieving.Actually Only 1 object will be created in this scenario and the constructor calls will be same as you have stated.

constructor call is required to initialize those members of the super classes which are derived from the super class in derived class.
As the data members which are being derived into the derived class need to be initialized by their respective constructors(constructors are not inherited).

In case of Abstract class ,its true that they can't be instantiated but if some class has extended it in that case the members of that abstract class derived into the Sub class need to be initialized by the constructor of Abstract class only.

Hope you understand my point.


Regards...

[chander shivdasani]

Just Remember this, When an Object is Created, its constructor is called. But when a constructor is called, it does not mean that an Object is created.

Consider the following scenario

class A {
int x;

A()
{ this(10);
}
A(int z)

{
x=z;

}

public static void main(String args[])

{
A x = new A();

}

}

In the above case, the default constructor calls the overloaded constructor.
So in all 2 constructors are called, but Number of Object created is 1.

[Seetharaman Venkatasamy]

Originally posted by chander shivdasani:
In the above case, the default constructor calls the overloaded constructor.
So in all 2 constructors are called, but Number of Object created is 1.

LOOKS GOOD

[Ankur Mahajan]

Thank you all for your replies.
I have understood the concept now.

[Gaurav tyagigaurav]

Hi Guys!!!
I had exactly the same doubt that is stated in the original Q. Didnt know where to look for. Thanks to Java Ranch found the soln. here. Java ranch rocks [ ]. I however in the mean time was wondering how could i write/test the code to find out how many objects get created. Any idea how can we modify the above code to find out the number of objects created?

Cheers
Gaurav

[James Tharakan]

how could i write/test the code to find out how many objects get created.

The simple way i think is to use a initialization blocks,Which runs every time when a class object is created.

class A
{  static int i;
   
   A(){}
   A(int x){}
   
   {  //initialization blocks
    i++;
    System.out.println("No of objects:"+i);
   }
}
 
 class test
 { 
   public static void main (String arg[])
   { 
      A a1= new A(2);
      A  a2 =new A();
    }
}