java - What is the main difference between primitive type and wrapper class?

Question

What is the difference between these two lines?

    int pInt = 500;

and

    Integer wInt = new Integer(pInt);

Or

    Integer wInt = new Integer(500);

Answer 1

None.

That's the exact same thing. In the first case you just have a supplementary variable.

Note that with autoboxing you rarely need to have both an int and an Integer variables. So for most cases this would be enough :

int pInt = 500;

The main case where the Integer would be useful is to distinguish the case where the variable is not known (ie null) :

Integer i = null; // possible
int i = null; // not possible because only Object variables can be null

But don't keep two variables, one is enough.