Паралельнрая обработка списка

public class ThreadSearch implements Callable<DefaultMutableTreeNode> {
    private List<DefaultMutableTreeNode> list = new Vector<DefaultMutableTreeNode>();
    
    public ThreadSearch(List<DefaultMutableTreeNode> subList) {
        this.list = subList;
    }
 
     public DefaultMutableTreeNode call() {
        int maxFlatNum = 0;
        int flatNum;
        DefaultMutableTreeNode biggest = null;
        for (int i = 0; i < list.size(); i++) {
            DefaultMutableTreeNode curNode = (DefaultMutableTreeNode) list.get(i);
            Object data = curNode.getUserObject();
            if (!(data instanceof House))
                continue;
            
            flatNum  = ((House) data).getFlatNum();
            if (flatNum > maxFlatNum) {
                maxFlatNum = flatNum;
            }
                 }
 
        return biggest;
    }
}
 
private void onThreadSearch() {
        System.out.println("Start of parallel search");
        long start = System.currentTimeMillis();
        DefaultMutableTreeNode node = getSelectedNode();
        if (node == null)
            return;
        
        DefaultMutableTreeNode biggest = null;
        Enumeration<DefaultMutableTreeNode> enm = node.postorderEnumeration();
        Vector<DefaultMutableTreeNode> vector = new Vector<DefaultMutableTreeNode>();
        while (enm.hasMoreElements()) {
            DefaultMutableTreeNode curNode = (DefaultMutableTreeNode) enm.nextElement();
            vector.add(curNode);
        }
        
        final ExecutorService service;
        final Future<DefaultMutableTreeNode> task1;
        final Future<DefaultMutableTreeNode> task2;
        service = Executors.newFixedThreadPool(2);        
        int mid = vector.size() / 2;
        task1 = service.submit(new ThreadSearch(vector.subList(0, mid)));
        task2 = service.submit(new ThreadSearch(vector.subList(mid, vector.size())));
        try {
            House biggest1 = (House) task1.get().getUserObject();
            House biggest2 = (House) task2.get().getUserObject();
            if (biggest1.getFlatNum() > biggest2.getFlatNum())
                biggest = task1.get();
            else
                biggest = task2.get();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (ExecutionException e) {
            e.printStackTrace();
        }
        service.shutdownNow();
        
        System.out.println(biggest);
        long end = System.currentTimeMillis();
        System.out.println("Duration: " + (end - start) + " (milliseconds)");
        System.out.println("End of parallel search");
        selectNode(biggest);
        ((AnyNode) biggest.getUserObject()).showDialog(false);
    }