The first thing we need to know is, " What is he barking at" ? and " Why is he barking" ? It' s usually easier to fix a problem if you know the reason for the problem in the first place. It' s usually easier to fix the ' cause' than it is to fix the ' response to the cause' .

If he' s barking for no apparrent reason, then it' s most likely to get your attention.
How much do you work him (train him)? How much time do you spend with him in play or just plain old ' socializing' ?

You say that he is 2 years old -- how long has he been doing the barking thing?
If he' s been doing it for a long time, then it may just be a habitual action on his part.