ListContainer list=(ListContainer)subscriberAcks.get(key);
for(Iterator i=list.iterator();i.hasNext();){
String id=i.next().toString();
AtomicInteger count=(AtomicInteger)ackContainer.remove(id);
if(count!=null){
if(count.decrementAndGet()>0){
ackContainer.put(id,count);
}else{
// no more references to message messageContainer so remove it
messageContainer.remove(id);
}