Add 'expand' button to JTree node that has no children?

Question

I'd like to add the 'expand' button to my JTree's nodes to indicate that they are expandable. The catch is that they have no children until the user clicks on them (due to processing that happens in the background).

Is there any way I can set a node as a parent or having children without it actually having children?

Thanks

Answer 1

It's possible using your own DefaultMutableTreeNode implementation overriding isLeaf():

Returns true if this node has no children.

Swing Tutorial: JTree explains it under 4.1 Dynamic Tree.

Answer 2

Have a fake child/child count and replace it with real children using TreeWillExpandListener