Concurrent iteration and deletion from Set in Java

Question

I have a pre-populated set of strings. I want to iterate over the items and while iterating, i need to "do work" which might also remove the item from the set. I want to spawn a new thread for each item's "do work". Please note that only some items are removed from the set during "do work".

Now i have the following question,

Can i achieve this by simply using Collections.synchronizedSet(new HashSet()); ? I am guessing this will throw up ConcurrentModificationException since i am removing items from the list while i am iterating. How can i achieve the above behavior efficiently without consistency issues ?

Thanks!

Answer 1

I would use an ExecutorService

ExecutorService es = Executors.newFixedThreadPool(n);
List<Future<String>> toRemove = new ARraysList<>();
for(String s: set)
   toRemove.add(es.submit(new Task(s)));
for(Future<String> future : toRemove()) {
   String s = future.get();
   if (s != null)
       set.remove(s);
}

This avoids needing to access the collection in a multi-threaded way.