How can i Dispose Dialog box From LWUIT Component

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Java

JavaSE

J2ME

I am developing one project using LWUIT, Midlet mobile Application. when I press number keys a dialog box will open. when i press the keys #,0,* Dialog should be close.
I am using Dialog.dispose() method to close dialog. But it is not working. Below is my Code. Can anyone tell me what is the problem in my code?

import com.sun.lwuit.Dialog;
import com.sun.lwuit.Dialog.*;
import com.sun.lwuit.events.ActionEvent;
import com.sun.lwuit.events.ActionListener;
import com.sun.lwuit.plaf.Border.*;
public class javaForm extends Component implements ActionListener
 {
    Dialog d;
    javaForm()
     {
       d=new Dialog(); 
     }

public void keyPressed(int key)
  {
    System.out.println("Key pressed :"+key);

      switch(key)
       {
               case 48:
                       d.show();
                       break;
               case 52:
                       d.dispose();
                       break;
               default:
                       break;
                    } 
      }
 public void actionPerformed(ActionEvent ae) 
   {
       throw new UnsupportedOperationException("Not supported yet.");
    }
 }