I'm getting a java.util.NoSuchElementException at high loads using
java.util.concurrent.CopyOnWriteArraySet.  I have one guess why and
would like to hear if it makes sense. Could this error occur because
two threads call the same instance?

For example, thread A executes i.hasNext() which returns true.  Then
thread B runs and happens to start executing at i.next().  When thread
A runs again, it will execute the i.next() but B has already advanced
the iterator to the end of the list.

I'm using CopyOnWriteArraySet to avoid synchronizing.  Do I have to
sync to avoid this issue?

Thanks for the opinions!

public class DistributionSet extends CopyOnWriteArraySet {

  private Iterator i;

 public void enqueue( Object message ) {

          for ( i = this.iterator( ) ; i.hasNext( ) ; ) {

           // .next() call is throwing an error - why?  either:
           // copy hasn't completed or .hasNext() has a different
count, or some listener was removed
           EventListener listener = ( EventListener ) i.next( );
            listener.eventObserved( message ) ;

       }
 }

  public  boolean add( EventListener consumer ) {
                 super.add( consumer );
        return true;  
   
   }
}