Role of Super Keyword in Java

In this article trying to explain the use of 'Super' keyword in Child class.

1. super() method @ Child class constructor
   

2. Super() with parameter method @ Child class constructor
   

3. Super()default/parameter method@ child class member method
   

4. Super keyword @child class Constructor
   

5. Super keyword @ child class member method

   Basically super keyword always refer the parent class object reference. We all know the parent of all java class is java.lang.Object. So when ever we create a java file(class) with out extending any class \,java compiler will do three basic operation.
   

1. Extend parent class java.lang.Object
   

2. if no constructor(default/Parameter) for the child class its include
   the default constructor.
   

3. If no super() method in constructor its include the super() in the
   first line of the constructor.

   Fact:
   

when ever we create the object for any User define class we always able to
access the methods from the Object class.Its does means always
create two object in Heap memory one is user define class and another
one is Object class.

S.No	Place of Super	Description	When executes	Where Not Include	Sample Code
1	Super() default method @ Child class Constructer	Super() its used for calling parent class constructer from child class constructer.In this case two object will be created . First Parent object will be created and than child object will be created.	While creating object reference for the child class.	It should be Present in first line of the child class constructer. Should not be two super() method statement in same constructer.	package superpck.blog; class Parent{ public Parent() { System.out.println("Creating Parent Object"); } } class Child extends Parent { public Child() { System.out.println("Creating Child Object"); } } public class SampleSuper { public static void main(String arg[]) { Child child=new Child(); } } output: Creating Parent Object Creating Child Object
2	Super() with parameter method @ child class.	Super() with Parameter it used for calling parent class constructer with parameter from child class constructer.In this case two object will be created . First Parent object will be created and than child object will be created. But we can initialize parent class instance variable from this.	while creating object for the child class	Same as S.No:1(Super() default method @ Child class Constructer)	package superpck.blog; class Parent{ Integer Parentage; public Parent() { System.out.println("Creating Parent Object"); } public Parent(int age){Parentage=age;} } class Child extends Parent { public Child() { System.out.println("Creating Child Object"); } public Child(int Parentage) { super(Parentage); } } public class SampleSuper { public static void main(String arg[]) { Child child=new Child(30); System.out.println("Parent age::"+child.Parentage); } } output: Parent age::30
3	Super() default/parameter method @ child class member method.	Error as : Constructor call must be the first statement in a constructor	-	Compile time error	-
4	Super keyword @ Child class constrcter	Its act as a parent class object reference from child class.Using super keyword we can call the parenet class member methods and instance variables only not constrcter.	Its depends upon the Instruction flow.	It can present any where and many time in both child class constrcter/ member methods.	package superpck.blog; class Parent{ Integer Parentage; public Parent() { System.out.println("Creating Parent Object"); } public Parent(int age){Parentage=age;} public void memberMethod() {System.out.println("Inside member method of Parent"); } } class Child extends Parent { public Child() { System.out.println("Creating Child Object"); } public Child(int Parentage) { super(Parentage); super.memberMethod(); super.memberMethod(); } } public class SampleSuper { public static void main(String arg[]) { Child child=new Child(30); System.out.println("Parent age::"+child.Parentage); } } Output: Inside member method of Parent Inside member method of Parent Parent age::30
5	Super keword @ child class member method.	Its act as a parent class object reference from child class.Using super keyword we can call the parenet class member methods and instance variables only not constrcter.	Its depends upon the Instruction flow.	It can present any where and many time in both child class constrcter/ member methods.	Refer s.No 4 sample.