Using Iterator

Question

My intention here is to implement a function that do something to a Collection. The function recusively "knock off" one element from the Collection and call recursively until it hits certain base case. Also, I would like my Collection argument untouched (order is not a concern, but at least all the element are there on return). Here is a test:
import java.util.*;
public class Test
     public static void test (Collection c) {
          for (Iterator iter=c.iterator(); iter.hasNext(); ) {
               Object b=iter.next();
               iter.remove();
               // revursively, do something with the
               // ``tail'' of the collection.
               c.add(b);     // cause ConcurrentModificationException
     public static void main(String argv[]) {
          LinkedList lst = new LinkedList();
          for (int i=0;i<10;i++) {
               lst.add (new Integer(i));
          System.out.println("Before: " + lst);
          test (lst);
          System.out.println("After: " + lst);
}I get ConcurrentModificationException and I understand that the problem is that I add within a Iterator loop.
If I remove the line:
c.add(b);my original list will be empty. How is this properly done? Thanks in advance.

Answer 1

You could create a new collection, rather than
modifying the existing one.My idea here is to avoid allocating and copying new
Collection.Don't worry about that. And you wouldn't be copying
it any more than you are now (you'd just be calling
add() on a different object).Good point here, I wasn't aware of this.
>
I need the remove as in the recursive step,What are you don't that's recursive? You referred to
recursion in a comment but what are you actually
doing?
I would
like to call the same function to the original listof
elements except for the one I have removed.So you're removing an element from the list, then
calling the same method recursively, which then also
removes an element, etc.? Are you doing a
combinatorics problem or something?Yes I am trying to find all the possible combination of an arbitrary collection of certain size 0<k<=c.size().
Thanks, I will go with backing up the Collection argument option.