🚀 go-pugleaf

Hi all,
I  make a class that extends JInternalFram, the class is called
MicraInternalFrame. When i create a new Frame i set the base class to be
MicraInternalFrame instead of JInternalFrame. At the time i click to the
design tab of the new frame i get this message...

1)Failed to create live instance for variable 'this'. MicraInternalFrame
2)class java.lang.NullPointerException null

I put below the MicraInternalFrame code...

import javax.swing.JInternalFrame;
import java.awt.event.*;

public class MicraInternalFrame extends JInternalFrame
   {
    //Data
members-------------------------------------------------------------
    static int openFrameCount=0;
    static final int xOffset=30, yOffset=30;


//Methods------------------------------------------------------------------
     public MicraInternalFrame(String title, boolean isResizable, boolean
isClosable, boolean isMaximizable, boolean isIconifiable)
      {
       super(title, //frame title
            isResizable,  //resizable
            isClosable,  //closable
            isMaximizable,  //maximizable
            isIconifiable); //iconifiable

                 //Set Default close operation
                 this.setDefaultCloseOperation(HIDE_ON_CLOSE );

       //Manage the Window position
       setLocation(xOffset*openFrameCount,yOffset*openFrameCount);
      }//contructor

    }//class MicraInternalFrame

Can anyonne tell me what is wrong? The class MicraInternalFrame or a wrong
configuration with the JB8?
Thank you for advance,  Kostas.