It definitely depends on the project. There are plenty of domains where hashmaps are useless, and some where half the things you do need one, and many in betwee

It definitely depends on the project. There are plenty of domains where hashmaps are useless, and some where half the things you do need one, and many in between. The in-between is the worst - if you need a hashset/hashmap just once, you'd still have to suffer through implementing one (O(n^2) is just not acceptable). But there is a bright side to this - hashmaps are pretty inefficient if a list could do, so the more you're pushed against using one, the more likely you are to have faster code :) (as long as you don't go the O(n^2) route, that is; also, hashsets are equally hard to implement manually as hashmaps)