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

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).