If you need external access to individual values of fields, use getters and/ or setters. If not, don't. Never use public fields. It's as simple as that! (Ok, it's never that simple, but it's a good rule of thumb).
In general you should also find that you need to supply a setter much less often than a getter - especially if you are trying to make your objects immutable - which is a Good Thing (but not always the best choice) - but even if not.
