Call this static method and it will happen.


/**
 * @param tree com.sun.java.swing.JTree
 * @param start com.sun.java.swing.tree.DefaultMutableTreeNode
 */
private static void expandTree(JTree tree, DefaultMutableTreeNode start) {
	for (Enumeration children = start.children(); children.hasMoreElements();) {
		DefaultMutableTreeNode dtm = (DefaultMutableTreeNode) children.nextElement();
		if (!dtm.isLeaf()) {
			//
			TreePath tp = new TreePath( dtm.getPath() );
			tree.expandPath(tp);
			//
			expandTree(tree, dtm);
		}
	}
	return; 
}