I've implemented a custom TreeModel that doesn't extend DefaultTreeModel. How do I get a JTree to update when the model changes?

Take a look at javax.swing.DefaultTreeModel. In particular, methods:

• addTreeModelListener()
• removeTreeModelListener()
• fireTreeNodesChanged()
• fireTreeNodesInserted()
• fireTreeNodesRemoved()
• fireTreeStructureChanged()
• nodesChanged()
• nodesInserted()
• nodesRemoved()
• nodeStructureChanged()

and the use of the listenerList declared in it.

You need to add similar event firing mechanisms in your model.

When you set your model to be the model that a JTree uses, the JTree adds itself as a TreeModelListener. Anytime you make a change in your model, fire an event (using one of the above methods that you'll create in your model) and the JTree will receive notification, and update itself.