JList.getModel() ClassCastException

Question

When I call JList<String>.getModel() and cast it to DefaultListModel<String> it gives me this exception.

Exception in thread "AWT-EventQueue-0" java.lang.ClassCastException: javax.swing.JList$4 cannot be cast to javax.swing.DefaultListModel

The code that throws it:

private JList<String> list = new JList<String>();
((DefaultListModel<String>) list.getModel()).addElement(...);

It doesn't do it every time though. Most of the time it works perfectly, but other times it throws this exception. I don't understand why this is happening. Is there anything I can do to stop this from happening?

Staphylorrhaphy

For better help sooner, post an SSCCE. – Abbreviation

For what its worth I thought the question was reasonable and complete, though this could be because of andrew's edits. – Jesseniajessey

@Jesseniajessey I can't even tell what Andrew edited. But I found the problem, it was calling the method setListData(E[]) changed the ListModel of the list. – Staphylorrhaphy

Answer 1

You should not assume it is a DefaultListModel. Use the interface ListModel. The JList is returning an internal implementation of ListModel.

If you need access to the underlying model you should create it, set it in the JList constructor and retain it yourself.

Jesseniajessey

retaining it is not necessary! see nikola despotoski's answer it is much more efficient! – Raceway

Answer 2

I experienced this issue. I found this simple workaround:

//----instantiation----

    JList mList = new JList();
    mList.setModel(new DefaultListModel());

    /*---- do whatever you want---- */

    //Retain it wherever you want with
    DefaultListModel model = (DefaultListModel)mList.getModel();

Voigt

I had the same problem... Creating it with a new default list model fixes everything. +1 – Blockbuster

Answer 3

If you are using NetBeans

1. Select your jList
2. In properties, click the model button
3. select the "Custom code" option
4. Write new DefaultListModel ()

Mystify

Answer 4

Before JList<String>.getModel(), you must initialize your object JList<String>.setModel(new DefaultModelList())

Spreadeagle

nothing new compared to one of the earlier answers, is there ;-) – Thormora