Might be useful specifying what university you are talking about. Some universities don't have any major specific subjects in the first semester or year. You can take that as a good or a bad thing lol, personally i would have hated last semester if i didn't have at least one subject relevant to the major i am doing. I think most (all?) of the universities offering flexible first year courses won't have, or won't require you to have any major specific subjects in the first year.
It also depends on your subject selection i guess, if you try and pick a heap of core subjects you won't have any wasted time. For example, at UTS i don't believe there is any flexible first year option but you would be able to get away with being undecided on a major for the first year if you choose your subjects carefully.