Removing a set from it self while iterating

Question

I've been stuck on this for awhile now. I am trying to remove elements of a set if they make a set criteria. However when iterating when I try to remove the element it fails.

I get the java.util.ConcurrentModificationException

private static void smallerSet(Set<Map<String, Int>> set){

    for (Map<String, Integer> map : set){

        for (String String : map.keySet()){

            if ( true){
                set.remove(map);

            }
            else{
                //System.out.println("test");


            }

        }
    }
}

Any advice would be greatly appreciated.

Duplicate of: http://stackoverflow.com/questions/1110404/remove-elements-from-a-hashset-while-iterating — Prakhar Verma, Apr 30 '17 at 09:15

score 1 · Answer 1 · answered Apr 30 '17 at 09:13

You cannot remove elements from a Collection while iterating over it with the enhanced for loop.

You should use an explicit Iterator and remove with the Iterator's remove() method:

Iterator<Map<String, Integer>> iter = set.iterator();
while (iter.hasNext ()) {
    Map<String, Integer> map = iter.next();
    for (String str : map.keySet()){
        if (some condition) {
            iter.remove();
            break; // you should probably break from the inner loop
                   // after removing an element
        } else {
            //System.out.println("test");
        }
    }
}

Removing a set from it self while iterating

1 Answers1