HashSet.remove() and Iterator.remove() not working

I was very curious about this one still, and wrote the following test:

import java.util.HashSet;
import java.util.Iterator;
import java.util.Random;
import java.util.Set;

public class HashCodeTest {
    private int hashCode = 0;

    @Override public int hashCode() {
        return hashCode ++;
    }

    public static void main(String[] args) {
        Set<HashCodeTest> set = new HashSet<HashCodeTest>();

        set.add(new HashCodeTest());
        System.out.println(set.size());
        for (Iterator<HashCodeTest> iter = set.iterator();
                iter.hasNext();) {
            iter.next();
            iter.remove();
        }
        System.out.println(set.size());
    }
}

which results in:

1
1

If the hashCode() value of an object has changed since it was added to the HashSet, it seems to render the object unremovable.

I’m not sure if that’s the problem you’re running into, but it’s something to look into if you decide to re-visit this.