Question

I have an array list of a array list and I want to make a separate view of it that will filter certain things from it and store it somewhere for later usage. I am planing on using an array list of array list and was wondering if array list has a way to be connected together where the change in one reflects another ? Any thoughts ? Its like an excel sheet and I would like to filter out certain numbers and I will display another view of the same sheet without really changing the original sheet. please help.

Answer 1

based on your explanation to the question, you can keep a sorted list.. and then do a sub set (explore navigable set and see how its implemented).. wrap you sub-set into a non-modifiable list or a new list whenever your are exposing it.
You can also a sorted/ navigable map if you expect to encounter duplicates.. so the value in the map can be number of duplicates. Now when you query this map for its head or tail to return the view, you can use the number of duplicates to achieve the desired list.

    NavigableSet<Integer> orderedSet = new ConcurrentSkipListSet<Integer>(Arrays.asList(new Integer[] {11, 20, 32, 14,
            5})); // or tree set if thread safety is not a concern.
    orderedSet.headSet(20); // will give you integers upto 20 i.e. [5, 11, 14]