Question

If the following code is possible:

Integer a = null;
int b = a;

Does it mean that a function returning a possible null value for an integer is a bad practice?

Edit 1:
There are several different opinions in these answers. I am not enough confident to choose one or another.

Answer 1

That code will give a NullPointerException when you run it. It’s basically equivalent to:

Integer a = null;
int b = a.intValue();

… which makes it clearer that it will indeed fail.

You’re not really assigning a null value to an int – you’re trying and failing.

It’s fine to use null as a value for an Integer; indeed often Integer is used instead of int precisely as a “nullable equivalent`.