About Question com.enthuware.ets.scjp.v6.2.82 :

[piotrkmiotczyk]

LinkedList container = new LinkedList();
"This is not valid because event though LinkedList has add() method, it does not have poll() method, which is used in the code."
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According to docs, LinkedList does have a poll() method.
http://docs.oracle.com/javase/1.5.0/doc ... dList.html
Not that I understand what it's for, since it seems to duplicate remove().

[admin]

You are right. Fixed.
thank you for your feedback!