When to use primitive and when reference types in Java

Question

In which case should you use primitive types(int) or reference types (Integer)?

This question sparked my curiosity.

Answer 1

If you want to setAttribute to session you have to use Object like Integer,Boolean,String in servlets. If you want to use value you can use primitive types. Objects may be null but primitives not. And if you want to compare types for primitives use == but objects use .equals because in object comparision == looks not values it looks if these are the same objects. And using primitives makes faster the code.

Answer 2

That really depends on the context. First prefer the primitive, because it's more intuitive and has less overhead. If it is not possible for generics/autoboxing reasons, or if you want it to be nullable, then go for the wrapper type (complex type as you call it).

Answer 3

One case in which Integer might be prefered is when you are working with a database where numerical entries are allowed to be null, since you wouldn't be able to represent a null value with an int.

But of course if you're doing straight math, then int would be better as others have mentioned due to intuitiveness and less overhead.

Answer 4

I dont think there is any rule as such. I would choose the types over primitives (Integer over int) when I write method signatures, Maps, collections, Data Objects that get passed around. As such I would still like to use Integer instead of int even inside of methods etc. But if you think that is too much trouble (to type extra "eger") then it is okay to use ints for local variables.

Answer 5

Rather than calling them "complex types", you'd be best served thinking Integer, Double, etc. as "Classes", and int, double, etc. as "primitives".

If you're doing any type of sophisticated math, the Class-based numeric representation like Integer and Double will be cumbersome and slow you down - many math operations can only be done with primitives.

On the other hand, if you're trying to put your numbers into collections like Lists and Maps, those collections can only contain objects - and thus you must use (or convert to) classes like Integer and Double.

Personally, I use primitives whenever I can get away with it, and only convert to the Class representations like Integer when it's time to do input or output, and the transport requires those representations.

However, if you aren't doing any math at all, and instead are just passing the values straight through your code, you might save yourself some trouble by dealing with the Class-based forms (like Integer) exclusively.