Irrespective of the amount of experience you have, it is not possible for us to be aware of and remember each and every facet of a programming environment. I have experienced it multiple times. 

Some of you will definitely say that I would be superficial for not having explored each and every facet of a language like Java if I claim to have sufficient experience using it. So, be it. But extending help to others has helped me, in turn, because I have been able to learn many new things that I did not have a chance to encounter during my project work.