EDIT

/**

 * @Deprecated unused class, remove?

 */

@Deprecated

    @Override

    public int compare(TreeNode<NamedArea> arg0, TreeNode<NamedArea> arg1) {

        return arg0.data.getLabel().compareTo(arg1.data.getLabel());

    }

 *

 * @Deprecated unused class, remove?

@Deprecated

    public NamedAreaTree() {

        NamedArea data = new NamedArea();

        TreeNode<NamedArea> rootElement = new TreeNode<NamedArea>();

        List<TreeNode<NamedArea>> children = new ArrayList<TreeNode<NamedArea>>();

        rootElement.setData(data);

        rootElement.setChildren(children);

        setRootElement(rootElement);

/*

        NamedAreaTree result = new NamedAreaTree();

        for (NamedArea area : areaList) {

            List<NamedArea> levelList = area.getAreaLevelPathList(area);

            result.merge(levelList);

        }

        return result;

    }

*/

    public void merge(List<NamedArea> areaList, Set<NamedAreaLevel> omitLevels){

        for (NamedArea area : areaList) {

            List<NamedArea> levelList = this.getAreaLevelPathList(area, omitLevels);

            mergeAux(levelList, this.getRootElement());

        }

    }

    public void sortChildren(){

        sortChildrenAux(this.getRootElement());

    }

    private void sortChildrenAux(TreeNode<NamedArea> treeNode){

        NamedAreaNodeComparator comp = new NamedAreaNodeComparator();

        if (treeNode.children == null){

            //nothing => stop condition

            return;

        }else{

            Collections.sort(treeNode.children, comp);

            for (TreeNode<NamedArea> child : treeNode.children) {

                sortChildrenAux(child);

            }

        }

    }

    private void mergeAux(List<NamedArea> areaHierarchieList, TreeNode<NamedArea> root) {

        TreeNode<NamedArea> child; // the new child to add or the child to follow through the tree

        //if the list to merge is empty finish the execution

        if (areaHierarchieList.isEmpty()){

            return;

        }

        //getting the highest area and inserting it into the tree

        NamedArea highestArea = areaHierarchieList.get(0);

        TreeNode<NamedArea> highestAreaNode = new TreeNode<NamedArea>(highestArea);

        //NamedAreaLevel level = highestArea.getLevel();

        //List<TreeNode<NamedArea>> children = root.getChildren();

        //if(children == null || !children.contains(highestAreaNode)){

        if (root.getChildren().isEmpty() || !root.containsChild(highestAreaNode)){

            //if the highest level is not on the depth-1 of the tree we add it.

            child = new TreeNode<NamedArea>(highestArea);

            root.addChild(child);

            //children.add(child);

        }else{

            //if the deepth-1 of the tree contains the highest area level

            //get the subtree or create it in order to continuing merging

            child = root.getChild(highestAreaNode);

        }

        //continue merging with the next highest area of the list.

        List<NamedArea> newList = areaHierarchieList.subList(1, areaHierarchieList.size());

        mergeAux(newList, child);

    }

    private List<NamedArea> getAreaLevelPathList(NamedArea area, Set<NamedAreaLevel> omitLevels){

        List<NamedArea> result = new ArrayList<NamedArea>();

        if (!omitLevels.contains(area.getLevel())){

            result.add(area);

        }

        while (area.getPartOf() != null) {

            area = area.getPartOf();

            if (!omitLevels.contains(area.getLevel())){

                result.add(0, area);

            }

        }

        return result;