/* Look for the minimal Index of all selected Elements */
int minSelectedIndex = Integer.MAX_VALUE;
TreeItemAdapter parentOfMinSelected = new TreeItemAdapter(tree);
/* For each selected Element */
Object[] selectedElements = selection.toArray();
for (Object selectedElement : selectedElements) {
Widget widget = findItem(selectedElement);
if (widget instanceof TreeItem) {
TreeItem item = (TreeItem) widget;
TreeItemAdapter parent = new TreeItemAdapter(item).getParent();