Re: how to delete a JList element

From:

thufir <hawat.thufir@gmail.com>

Newsgroups:

comp.lang.java.help

Date:

Sat, 21 Jun 2008 21:01:21 GMT

Message-ID:

<B_d7k.19222$kx.6696@pd7urf3no>

On Sat, 21 Jun 2008 02:51:41 +0000, Roedy Green wrote:

ListModel does not have any sort of remove method.

However DefaultListModel does. If your model were a DefaultListModel
then you could cast to (DefaultListModel) or simply hold onto a
reference to it and use its removeElementAt method.

This seems to give a NullPointerException, as below, because the backing
collection is a DefaultListModel:

java.lang.NullPointerException
        at a00720398.view.NewJFrame.displayGuest(NewJFrame.java:458)
        at a00720398.view.NewJFrame.showGuest(NewJFrame.java:435)
        at a00720398.view.NewJFrame.showGuest(NewJFrame.java:486)
        at a00720398.view.NewJFrame.access$000(NewJFrame.java:13)
        at a00720398.view.NewJFrame$1.valueChanged(NewJFrame.java:332)
        at javax.swing.JList.fireSelectionValueChanged(JList.java:1765)
        ...

thufir@arrakis:~/bcit-comp2611-project2$
thufir@arrakis:~/bcit-comp2611-project2$ head src/a00720398/view/
NewJFrame.java -n 481 | tail -n 10

   private void deleteGuestActionPerformed(java.awt.event.ActionEvent
evt)//GEN-FIRST:event_deleteGuestActionPerformed
   {//GEN-HEADEREND:event_deleteGuestActionPerformed
      int i =guestList.getSelectedIndex();
      BedAndBreakfast bnb = BedAndBreakfast.getInstance(); //the
"database"
      System.out.println("delete guest \t" + i + bnb.getGuests().get(i));
      ((DefaultListModel)(guestList.getModel())).removeElementAt(i);
      System.out.println("bnb\n" + bnb.toString());
   }//GEN-LAST:event_deleteGuestActionPerformed

thufir@arrakis:~/bcit-comp2611-project2$

So, I think that I'll have to change BedAndBreakfast.getGuests() not to
return a DefaultListModel, which I assume is causing the
NullPointerException, but rather have it return, for instance, a Vector.

yes/no?

thanks,

Thufir