MindQ question #47

[Nain Hwu]

47. In the list below, which subclass(es) of Component cannot be directly instantiated:
a) Panel
b) Dialog
c) Container
d) Frame
The answer is c.
I thougt b should be the answer, since Dialog would need a
Frame to help instantiate it.
I am confused. :confused So I wrote a code to test it as below.
It compiled without error and ran.

import java.awt.*;
import java.applet.*;
public class A extends Applet {
   public void init() {
Container Ax = new Container();
Ax.setLayout(new GridLayout(2,1));
Ax.add(new Button ("Hello"));
add(Ax);

   }
}

Any thought?

[Jane Griscti]

Hi Nain,
Think you're right. All the Dialog constructors take an 'owner' as an argument.
The question is a little misleading, as you can instantiate a Dialog if you pass in an 'owner'. Perhaps they mean which one can't stand on it's own?
------------------
Jane Griscti
Sun Certified Programmer for the Java� 2 Platform

[Nain Hwu]

Thanks, Jane. It clears my doubt.