Question

I am confused about when to use primitive vs. non-primitive(?) types (i.e. int vs. Integer) in Java. I realize that in some places you can’t use primitive types (for example when making use of generics). But what about in “normal” code? Is there a performance penalty for using non-primitive types? What about when working with Android?

***My question is very similar to this question, which was discovered by one of the posters below. The answers to the linked question give additional insights into this question, which are not covered below.

*** “non-primitive” types are officially referred to as reference types.

Answer 1

Short answer: An int is a number; an Integer is a pointer that can reference an object that contains a number. Using Integer for arithmetic involves more CPU cycles and consumes more memory. An int is not an object and cannot be passed to any method that requires objects (just like what you said about Generics).