sample experimanting mock code(consturctor related)

[Arjun Srivastava]

   
class ClassA {
 public int i;
// ClassA() {}  //line1
 ClassA(int i) {
 this.i = i;}
}
 public class Main extends ClassA {
 private Main(int i) {
 super(i);  //line2
 }
 public static void main(String...a) {
 Main ext = new Main(420);
 System.out.print(ext.i);
 }}

above code compiles fine.
we know if we are invoking the subclass overloaded constructor,then super-class no arg constructor will be
invoked first, and if super-class no arg constructor is not there, then it will be a compiler error.
if we commented out line2 ,we have to defined superclass no arg constructor(i.e. uncommented out line 1), othervise it
gives a compiler error,what is the logic behind it?
why we don't need no arg. super-class constructor(default) here ,as we are instantiating subclass object(with arg.)?

[Gari Jain]

Arjun

within a constructor the first line should be either a call to this() or super()

and when the compiler doesnt find such a call, it inserts super() by default.

in your code the Main() constructor already has a call to super(arg) and thus super() will not be invoked.
try removing the super(arg) line and you will see that the code will not compile.

Refer to K&B for detailed description about this.(very nicely explained in that book)

[Arjun Srivastava]

yeah,thanks garima for clearing my query

[Gari Jain]

Happy to help