private void addElement(String element, String contact) {
        int indexOfItem = getItemIndexByElementName(element);
        if (indexOfItem == -1) { // add a new element
            TreeItem item = new TreeItem(tree, SWT.NONE);
            item.setText(element);
            if (!"-1".equals(contact))
            {
                TreeItem litem = new TreeItem(item, SWT.NONE);
                litem.setText(contact);
            }
        } else { // add a contact to existing element
            TreeItem litem = new TreeItem(tree.getItem(indexOfItem), SWT.NONE);
            litem.setText(contact);
        }
    }