This week's book giveaway is in the OCMJEA forum. We're giving away four copies of OCM Java EE 6 Enterprise Architect Exam Guide and have Paul Allen & Joseph Bambara on-line! See this thread for details.
poll method Retrieves and removes the head of this queue . so when you remove an element from collection at the time of looping you get ConcurrentModificationException. to remove an element while looping use Iterator instead.