can parent class constructor be invoked using this operator?

[Jyotsna Umesh]

Which of the following statements are true?
[a] Parent class constructors are not inherited to subclass
[b] Constructors can be overloaded but not overridden
[c] A parent class constructor can be invoked using this operator
[d] Any method may contain a call to this or super
The ans. given to above code is a,b and c where as i think c option is vague becoz if parent class is meant be super class then its constructor can be invoked by using super not this.
Please clarify
Thanks
Jyotsna

[Thomas Paul]

Actually you can do this:

<font size="+0">
public class Child extends Parent
{
    
    public Child(int i) 
    {
        this.super(i);
    }
}

[Anshul Manisha]

I tried to execute the following code in JBuilder

class JTestA{
JTestA(int x)
{
  System.out.println("inside A #" + x);
}
}
class JTestB{
JTestB(int x)
{
  System.out.println("inside B #" + x);
}
}
class JTestC extends JTestA{
JTestC()
{
  this.super(0); //line 26
  JTestB bObj = new JTestB(9);
}
}
public class Java0601 {
public static void main(String args[])
{
  JTestC cObj = new JTestC();
}
}

when I tried to compile it I got the following error

"Java0601.java": Error #: 479 : illegal qualifier; class anshul.JTestA is not an inner class at line 26, column 8

thanks

------------------
AM
[e-mail]
[This message has been edited by Anshul Manisha (edited June 15, 2001).]

[Manfred Leonhardt]

Hi Anshul,
Something is wrong with your JBuilder ...
If you are trying to argue with Tom then give it up. He is correct. Try the following code to prove it (try it outside of JBuilder).

class A2
{
  public A2( int i )
  {
    System.out.println( "Inside A2 ..." );
  }
};
public class A extends A2
{
  public A()
  {
    this.super( 2 );
  }
  public static void main( String[] arg )
  {
    A a = new A();
  }
}

Regards,
Manfred.

[Thomas Paul]

Compiled clean in version 1.2. Error in version 1.3

[Anshul Manisha]

So what is the final conclusion? Tom did you also get the same compilation error as the one I got with JBuilder4. Incidently the JVM used by JBuilder is 1.3.0-c

[Thomas Paul]

Yes, I got the same error when I compiled using 1.3. The final verdict? I would say that this.super is an odd construct anyway and since it doesn't work in the current release version of the JDK that this.super is an illegal construct. I haven't had a chance to see if the JLS says anything about it.

[Jyotsna Umesh]

Originally posted by Thomas Paul:
Yes, I got the same error when I compiled using 1.3. The final verdict? I would say that this.super is an odd construct anyway and since it doesn't work in the current release version of the JDK that this.super is an illegal construct. I haven't had a chance to see if the JLS says anything about it.

Thanks Thomas, so in this circumstances should we select the option c also?
Jyotsna

[Anand Mishra]

I don't know if it has to do with 1.2 or 1.3, JBuilder3 gives me a compler error for either 1.2 or 1.3 when I use this.super(). It works fine when I use just super() .

[Thomas Paul]

Originally posted by Jyotsna Umesh:
Thanks Thomas, so in this circumstances should we select the option c also?

I have a feeling you won't see anything like that on the certification exam but the answer would really depend on what (if anything) the JLS says.

------------------
Tom - SCJP --- Co-Moderator of the Programmer Certification Forums