This week's giveaway is in the EJB and other Java EE Technologies forum. We're giving away four copies of EJB 3 in Action and have Debu Panda, Reza Rahman, Ryan Cuprak, and Michael Remijan 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.