CODEWITHSUNDEEP
javaswingjlist
Stripies
Stripies

Reputation: 1267

JList.getModel() ClassCastException

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?

Upvotes: 8

Views: 16985

Answers (4)

SandroMarques
SandroMarques

Reputation: 6544

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 ()

jList custom code

Upvotes: 10

Black_Zerg
Black_Zerg

Reputation: 87

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

Upvotes: 1

Nikola Despotoski
Nikola Despotoski

Reputation: 50588

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();

Upvotes: 16

ditkin
ditkin

Reputation: 7054

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.

Upvotes: 6

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