Can I add a tree as an element in a JList and be able to display the expanded tree in the JList?

Sandip Chitale

Not directly. However you could follow the same strategy as the one used by JTreeTable implementation that can be found here -

The main principle behind it is use of a JTree as the cell renderer of a column in the JTable. Also a composite model of TableModel and TreeModel is used. You will have to do similar thing. i.e. JTree as a cell renderer for the JList backed by a composite of ListModel and TreeModel.