Infinite loop on sets folding

Question

I have a task to remove any set from the collection that is wholy included into some other set:

private static Set<Set<String>> foldSets(Set<Set<String>> sets) {
    OUTER:
    while (true) {
        for (Set<String> s1 : sets) {
            Set<Set<String>> toRemove = new HashSet<>();
            for (Set<String> s2 : sets) {
                if (s1.size() > s2.size() && s1.containsAll(s2)) {
                    toRemove.add(s2);
                }
            }
            if (!toRemove.isEmpty()) {
                sets.removeAll(toRemove);
                continue OUTER;
            }
        }
        return sets;
    }
}

OUTER loop goes infinite, while common sense tells me it's impossible under any circumstances. That happens because removeAll method doesn't remove anything from sets.

This riddle drives me crazy. Please, help to solve.

Similar problem: Why won't it remove from the set?

Answer 1

It could be a permission problem.

If you Overrided it, it would be good to see your "removeAll" method, anyways. You are trying to delete folders, right?

If you can't solve it I have a working code that recursively removes folders and files inside it.

Here is the sample.

If you are not deleting folders and it's just a String stuff debug it and tell us which step is not working at all.

Answer 2

Solved!

It was a hash problem. Sets added to sets were modified after adding. That rendered them invisible for removeAll method, which relies on hash to lookup items.

Quite a riddle, nevertheless.