Session 12:- Constructor Chaining

 Why we use Constructor Chaining:-

•  Any constructor of a class whether they are default or custom first executable statement is calling its immediate parent class, zero parameterized constructor.
• The constructor chaining is required to initialize the resource or state of parent class. 
•   In any constructor when we explicitly provide. “this” or “super” than implicitly super will be destroyed. 

NOTE:-

•   We can’t have more than one “super” or we can’t have  more than “this”.
•  We can’t have more than one “super” and one “this” at a same time. 
• Constructor can’t call the same class constructor or super class constructor by name rather it has to call by using “super” or “this”.
• “Super” or “this” must be first executable statement of the in case of constructor.

Example:- Constructor Chaining By using Super and this Keyword 
 
public class Grandfather {

public Grandfather(){

System.out.println ("Grandfather Constructor ");

 }

 }

public class Father extends Grandfather {

public Father(){

System.out.println("Father constructor");

 }

 }

public class Child extends Father {

public Child(){

System.out.println("Child constructor");

   }

  }

public class Guldu {

public static void main(String[] args) {

   new  Child();

}}  

 OUTPUT:- 

 Grandfather constructor 

 Father constructor 

 Child constructor

NOTE:-   

• All the classes in java are the child class of java.lang. Object  
• i.e. Object is most parent class
• In java the moment when write class it automatically inherit java.lang. Object