ConcurrentModificationException

[angel]

HashMap<Long, Long> activeUsers = core.getUsers();
				Iterator<Entry<Long, Long>> it = activeUsers.entrySet().iterator();
				while(it.hasNext()){
					Map.Entry<Long,Long> entry = (Map.Entry<Long,Long>) it.next();
					log.info(entry.getKey()+"      "+entry.getValue());}

这个在it.next的时候报
java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
at java.util.HashMap$EntryIterator.next(Unknown Source)
at java.util.HashMap$EntryIterator.next(Unknown Source)
at com.dgF.sms.core.thread.DealSubmitSMSThread.run(DealSubmitSMSThread.java:38)