How do I know which object is selected?

Hi,
I have a JTree which is made up of nodes (Tests) and leaves(test steps) when the user clicks on the tree I need to know which item has been selected. However my problem is I am having to cast the selected node to enable me to use it, but obviously need to cast it inot the correct object. I have tried to create a superclass which both the test and the testsep class extend but am still stuck on how I can test to see which type the returned object really is.
Thanks

//for each test object add a new tree node
for( int i = 0; i < testControl.getSize(); i++ )
        {
            Test thisTest = testControl.getTest( i );
            String name = thisTest.getTestName();
            DefaultMutableTreeNode node = new DefaultMutableTreeNode( name );
            node.setUserObject( thisTest );
            root.add( node );
            
            //add children to the node
            for( int m = 0; m < thisTest.getSize(); m++ )
            {
                TestStep thisTestStep = thisTest.getTestStep( m );
                String stepName = thisTestStep.getStepName();
                DefaultMutableTreeNode step = new DefaultMutableTreeNode( stepName );
                step.setUserObject( thisTestStep );
                node.add( step );
            }
}
//add a tree listener
tree.addTreeSelectionListener(new TreeSelectionListener()
{
    public void valueChanged(TreeSelectionEvent event)
    {
            //the user selects a tree node
            TreePath path = tree.getSelectionPath();
            
            if( path == null ) return;
            selectedNode = (DefaultMutableTreeNode) path.getLastPathComponent();
            
            //cast into super class object
            selectedItem = (TestCase)selectedNode.getUserObject();
            
    System.out.println("TestMgmt selected: " + selectedItem );
            fieldDescription( selectedItem );
    }
});

You can use either of these expressions:
selectedNode.isLeaf()
selectedNode.getUserObject() instanceof TestCase
You do need to find this out before cast to TestCase.
[ April 07, 2004: Message edited by: Steve Lovelace ]

Thanks Steve