Is Superclass Object created everytime a subclass is instantiated? [duplicate]

This question already has an answer here:

This is a two part question :

PART #1 :

public class Test {

public static void main(String args) {

System.out.println("Main Started");
Child c = new Child(); //Instantiating Child Class
System.out.println("Main Ended");
}

}

class Father{

Father(){ //Father Class Default Constructor
System.out.println("I am in Father");
}

void show(){
System.out.println("Hello World");
}
}

class Child extends Father{

Child(){ //Child Class Default Constructor
System.out.println("I am in Child");
}
}


Output :

Main Started
I am in Father
I am in Child
Main Ended


This is what i know is happening at compile time

class Child extends Father{

Child(){ //Child Class Default Constructor
super();
System.out.println("I am in Child");
}
}


here my question is, since it is going to the default constructor of the Father Class before executing the default constructor of Child Class, is there an object created for Father?

Father

Child

Father

if so, then what is it getting assigned to? or is it similar to anonymous object like new Father();. Is an Object created EVERYTIME a constructor is called?

new Father();

Object

PART #2

Every single time i create an object for the Child Class, the default constructor of the Father Class will be called using super(); within Child().

Child

Father

super();

Child()

What will happen when I am trying to invoke any method from Father using the Child object? will it again create an anonymous object for Father, use the object for execution then leave it for Garbage Collector to take care of?

Father

Child

Father

Garbage Collector

Because of so, wouldn't this lead to tons of memory wastage simply because we tried to access the members of supper class multiple times.

How will the memory management take place in the above mentioned scenario?

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new

new

File

null

File(String path){..}

1 Answer
1

When you create a Child instance you aren't creating an additional Father instance. The Child instance is also a Father instance, since Child extends Father. Child is a specific type of Father.

Child

Father

Child

Father

Child

Father

Child

Father

One neat way of showing this is to print System.identityHashCode in both classes, and seeing that both the Father and the Chilld constructors relate to the same memory address:

System.identityHashCode

Father

Chilld

public class Test {
public static void main(String args) {

System.out.println("Main Started");
Child c = new Child(); //Instantiating Child Class
System.out.println("Main Ended");
}

}

class Father{

Father(){ //Father Class Default Constructor
System.out.println("I am in Father in address " + System.identityHashCode(this));
}

void show(){
System.out.println("Hello World");
}
}

class Child extends Father{

Child(){ //Child Class Default Constructor
System.out.println("I am in Child in address " + System.identityHashCode(this));
}
}


And an example output:

Main Started
I am in Father in address 2001049719
I am in Child in address 2001049719
Main Ended


Super Class

Child

Father

this