How to compare multiple arraylists ....

Question

with different length?
Imagine you´ve got one ParentArrayList, which contains one or more ArrayLists as elements. The (Child)ArrayLists contains multiple String elements of different size.
Here is a small Graphic on this:
Parent_ArrayList
####Child_ArrayList_1->element1->element2->element3
####Child_ArrayList_2->element1->....elementn
####Child_ArrayList_n->element1->element2->element3
E.g.:I have to compare all the elements of the child_arraylists_1 with child_arraylists_2 , write all elements which are euqal into an other temparrayList.Then Compare temp arraylist with elements of Child_ArrayList_n and write it back into the temp_arraylist.
I hope I could explain my problem?!?
Thank you for any suggestions?!

Answer 1

Hi Mehmet,
     private final static String[][] initial_data = {{"1", "2", "3", "5"},
                                                                 {"2", "3", "5", "8", "12"},
                                                                 {"3", "5", "7", "12", "20"},
                                                                 {"4", "7", "3", "9", "5", "2"},
                                                                 {"5", "9", "2", "7", "9", "0", "3"}};
     private final static List Parent_ArrayList = new ArrayList();
     static {
          for (int i = 0; i < initial_data.length; i++) {
               final List Child_ArrayList = new ArrayList();
               for (int j = 0; j < initial_data<i>.length; j++) {
                    Child_ArrayList.add(initial_data<i>[j]);
               Parent_ArrayList.add( Child_ArrayList );
               Set common = null;
               for (Iterator iter = Parent_ArrayList.iterator(); iter.hasNext();) {
                    List element = (List) iter.next();
                    Set tempSet = new HashSet(element);
                    if(null==common) {
                         common = tempSet;
                    } else {
                         common.retainAll(tempSet);
common will contain common string from all children.
Best regards, Maksim Rashchynski.