Inner Classes Mock question doubt 2

[Hardik Raja]

Hello Friends,

This is a question from K & B Book, Chapter Inner classes, Page 666

4. Given:
class Boo {
Boo(String s) { }
Boo() { }
}
class Bar extends Boo {
Bar() { }
Bar(String s) {super(s);}
void zoo() {
// insert code here
}
}
Which create an anonymous inner class from within class Bar? (Choose all that apply.)
A. Boo f = new Boo(24) { };
B. Boo f = new Bar() { };
C. Boo f = new Boo() {String s; };
D. Bar f = new Boo(String s) { };
E. Boo f = new Boo.Bar(String s) { };
 
Answer:
 
B and C. B is correct because anonymous inner classes are no different from any other
class when it comes to polymorphism. That means you are always allowed to declare a
reference variable of the superclass type and have that reference variable refer to an
instance of a subclass type, which in this case is an anonymous subclass of Bar. Since Bar
is a subclass of Boo, it all works. C uses correct syntax for creating an instance of Boo.
 
A is incorrect because it passes an int to the Boo constructor, and there is no matching
constructor in the Boo class. D is incorrect because it violates the rules of polymorphism;
you cannot refer to a superclass type using a reference variable declared as the subclass
type. The superclass doesn't have everything the subclass has. E uses incorrect syntax.

My question is regarding the foll option....

A. Boo f = new Boo(24) { };
If there were a constructor in BOO that takes an int..would that constructor
be invoked ( in Constructor chaining ), when instance of anonymous subclass of BOO is created.

Can anyone please give their suggestions on the above problem.Thank you in advance.

Regards,
Hardik.S.Raja

[Mark Uppeteer]

go ahead and try it! put a println in that constructor and see.

[Hardik Raja]

Ya that constructor is getting innvoked..

Thanks..