put-take-block,offer-poll-noblock-false-null
Error和RuntimeException 及其子类都是未检查的异常(unchecked exceptions)
所有其他的Exception类都是检查了的异常(checked exceptions).
NullPointerException,IndexOutOfBoundException, ClassCastException
IllegalArgumentException
自定义EventLoopException,codecException extends RuntimeException
http://www.iteye.com/topic/694591