getting access to grandfather's constructor

[Shay Gaghe]

Hi
I have a class named Father the extends Grandfather , inside this class Father I have an inner class named Son, how can I get access the Grandfather constructor from the Son class?(code please)
Thanks
Shay Gaghe

[Manish Hatwalne]

Originally posted by Shay Gaghe:
I have a class named Father the extends Grandfather , inside this class Father I have an inner class named Son, how can I get access the Grandfather constructor from the Son class?(code please)

This is the code for constructor calling from Son. However, if Father extends GrandFather and Son is a non-static inner class, its creation by default will call all the constructors from top order; GrandFather, Father and then Son. Is this what you want?

<font size="+0">
class GrandFather
{
public GrandFather()
{
System.out.println("GrandFather");
}
}
public class Father extends GrandFather
{
public Father()
{
System.out.println("Father");
}
public static void main(String args[])
{
Father.Son obj = new Father().new Son();
}
public class Son
{
public Son()
{
Father.super();
}
}
}

HTH,
- Manish

[Shay Gaghe]

Hi
In my particular case I have class named A that extends Jlabel, and in the A I have another class named B that extend Jlabel as well. in order to perform image displaying from B I meant to call (by super(image) to the Jlabel constructor but I cant because A is the superclass, how can I do such a performance calling the Jlabel constructor(which is the A superclass)?
(I don�t know why its not calling the B superclass which is jlabel as well, I try it but I receive compiling error)
Thanks

[Manish Hatwalne]

Originally posted by Shay Gaghe:
In my particular case I have class named A that extends Jlabel, and in the A I have another class named B that extend Jlabel as well. in order to perform image displaying from B I meant to call (by super(image) to the Jlabel constructor but I cant because A is the superclass, how can I do such a performance calling the Jlabel constructor(which is the A superclass)?
(I don�t know why its not calling the B superclass which is jlabel as well, I try it but I receive compiling error)

OK.
In this case you need to ensure 2 things
1) Class A has default, no parameter constructor, else call its parameterized constructor appropriately.
2) While calling super(Icon image) in the inner class constructor, image shouldn't be an instance variable of the inner class B, or its outer class A.
HTH,
- Manish

[This message has been edited by Manish Hatwalne (edited October 15, 2001).]

[Shay Gaghe]

Hi Manish
itried to run this code and i got the following error:

class GrandFather{
  public GrandFather(){
    System.out.println("GrandFather");
  }
}
public class Father extends GrandFather{
  public Father(){
      System.out.println("Father");
  }
  public static void main(String args[]){
      Father.Son obj = new Father().new Son();
  }
  public class Son{
    public Son(){
      Father.super();
    }
  }
}

errors:
"Father.java": Error #: 300 : variable Father not found in class Father.Son at line 18, column 7
"Father.java": Error #: 479 : illegal qualifier; class java.lang.Object is not an inner class at line 18, column 14

thanks

[Shay Gaghe]

Hi , look in this please:

public class Balloon extends JPanel{
  BLabel blabel = new BLabel();
  public Balloon(){
    setLayout(new BorderLayout());
    add(blabel);
  }
  class BLabel extends JLabel{
    public BLabel(){
      // how can i call to JLabel constructor from here
      repaint();
    }
    public void paintComponent(Graphics g){
      g.fillOval(0,0,100,100);
    }
  }
}

thanks

[Peter den Haan]

Originally posted by Shay Gaghe:
I have a class named Father the extends Grandfather , inside this class Father I have an inner class named Son, how can I get access the Grandfather constructor from the Son class?(code please)

You can't, except by creating a new Grandfather object. There is no way to directly call a constructor, with one exception: in the very first line of a constructor, you can call a different constructor in the same class by calling this() or the superclass constructor by calling super().
- Peter

[Manish Hatwalne]

The first code you had posted (Father - Son) compiled on machine w/o any problem. (win 2k, JDK 1.3)
As for your second code snippet, since outer class extends JPanel and inner class extends JLabel, it shouldn't be a problem. Like Peter said you'll neeed to call it in the constructor as the very first line, with a value which is not an instance variable of that class.
Here is a code snippet I have tried on my machine which compiles w/o a problem. Of course, you'll need to make sure that Icon img in the outer class holds a proper value.

<font size="+0">
import javax.swing.*;
import java.awt.*;
public class Balloon extends JPanel
{
   Icon img; //do assign some proper value;
   BLabel blabel = new BLabel(img);
   public Balloon()
   {
      setLayout(new BorderLayout());
      add(blabel);
   }
   class BLabel extends JLabel
   {
       public BLabel(Icon img)
       {
         [B]BLabel.this.super(img); // or super(img)[/B]
         // how can i call to JLabel constructor from here
         repaint();
       }
       public void paintComponent(Graphics g)
       {
          g.fillOval(0,0,100,100);
       }
    }
 }

Let us know if it helps,
- Manish
[This message has been edited by Manish Hatwalne (edited October 15, 2001).]