DefaultListModel and setElementAt()

Question

I am pulling objects out of a vector and inserting them into a DefaultListModel within a JList. I want to be able to replace what is in the index already (or just add it if nothing is there). Problem is, unless I define a size for the DefaultListModel, it gives me an ArrayIndexOutOfBounds excpetion when it get to the setElementAt() line. Here is my code:
        String target=separate.nextToken().trim();
        System.err.println("target: "+target);
        String source=separate.nextToken().trim();
        System.err.println("source: "+source);
        //dataListModel.setSize(5);
        Vector targetVec=calculateValue("set", target);
        Vector sourceVec=calculateValue("set", source);
        for (int j=0; j < sourceVec.size(); j++)
          //dataListModel.ensureCapacity(j+1);
          System.err.println("sourceVec: "+(String)sourceVec.get(j));
          System.err.println("index: "+j)
          dataListModel.setElementAt(sourceVec.get(j), j);
        }I tried using ensureCapacity() instead of setting the size but that did not work. I also tried
    if the listModel is empty
       add the element
    else
       setElementAt(blah, blah)but everytime it throws the OutOfBounds exception! What am I doing wrong? I cannot set the size as I cannot have any empty indices since I need the user to be able to delete the last item in the list, and if I set the size they have all the empty indices to delete first!! If I just use add(), then of course anything already in an index, just gets moved up. There is a possibility I will need to keep some of what is already in the list.

Answer 1

Thanks for your reply. Unfortunately I cannot call removeAllElements() as I may need what is in the DefaultListModel, here is what I mean:
    for (the number of user instructions)
       get the index supplied by user
            if it is empty
                add the value specified by user at the index specified by user
             else
                 replace index(value specified with user) with another value specified by usermeaning that the user could specify replacing index 1 and 3 for example with new values, but if there were values in indices 0, 2, 4, 5 these would need to remain (and in fact are visible to the user in the DefaultListModel as are the new values inserted by the user), thus removeAllElements() would delete needed information. Is this clearer?