Referring to parent class in Java

Question

I want to know if it possible to use This() To reffer MotherClass, Calling My motherClass A and executing it from my Child Class B. witch one is correct ?

Class A { A(){ System.out.println("hello");}

Class B extends A { this() ;  B(){System.out.println("World");}}

OR 

class A {
 Class B { this(); B(){System.out.println("World");} }
}

I want when to Call Class B it show Me (HelloWorld);

Sorry for my bad english.

Answer 1

Calling this() is meaningless unless you are calling it in a constructor and which means to call a constructor overload for this current class (if one exists). Please see this tutorial for the details on this. To call a super class's methods, again use the super keyword.

Incidentally, your code still doesn't compile. Please understand that you can't be careless when coding -- the compiler won't let you, and neither should you be when creating and posting code for questions here.

Answer 2

Create a file - parent.java

public class parent {
    parent(){
        System.out.println("Hello");
    }
}

---

Create another file - child.java

public class child extends parent {
    child(){
        super();
        System.out.println("World");
    }

    public static void main(String[] args) {
        child c = new child();      
    }
}

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Creating an instance of child class will first call the parent class constructor and then the child class constructor; resulting in the o/p you are looking for.