Which one to use, int or Integer

To my mind, the choice between declaring something as int or Integer simply comes down to whether null is a valid value for it or not. Autoboxing (and autounboxing) will take care of any conversion issues where the number simply must be one type or another. Performance (as has been pointed out) is also unlikely to be noticable in almost all cases.

Besides, int should be the natural choice, and is likely to be the most performant should that be an issue anyway. If you need to be able to store nulls, then you have to use Integer (and also ensure that no null references are auto-unboxed for a method that takes simply ints as this will result in a NullPointerException).

You should really make your decision based on- what you need your object to do, rather than the performance costs. Deciding based on performance should be done, once a speed issue has been identified with a profiler - the root of all evil and all that.

Look at some of the features of both and use that for your decision, e.g.

• Integer can be null, int cannot. So is the int in the DB a Nullable field?
• Do you need access to the Integer class methods?
• Are you doing arithmetic?

Personally, I always opt for the primitive over the wrapper. But that's just a preference thing, rather than based on any technical merit.

Integer is a better option, as it can handle null; for int, null would become 0, silently, if resultSet.getInt(..) is used. Otherwise, it might throw some exception, something like, "Unable to set null to a primitive property".

Performance is of little concern here.

• if you choose int, you will end-up adding extra handling code; and that wouldn't benefit you much. Your code will not be clean and straight-forward, lot of boiler-plate code, and you wouldn't even gain performance.
• let me make it clear, for databases, null is not same as zero. Sometimes you end-up entering 0, where null was intended. Imagine the case where user submitted a form, and doesn't supply any value for int. You will end up getting 0 by default. It makes sense, or does that really, when that field is not null in the database.