merge two arraylist lists in list1 while it remain sorted

Question

In my assignment the third step is to Call the method merge to merge the two lists in list1 so that the list1 remains sorted.

I write my code but it

Answer 1

After you merge the lists, call sort method as below.

Collections.sort(list1); // carries out natural ordering.

If you need a customized sorting, use Comparator object

Collections.sort(list1, comparatorObject);

Check Comparator example for more details.

Here is your modified code:

 public static void merge (ArrayList list1, ArrayList list2)
 {
    list1.add(list2); //merges list 2 to list1
    Collections.sort(list1); //natural ordering
 }