What is the difference between private modifier position in a Scala class declaration?

Question

Suppose I have two classes:

private[example] class PoorInt    extends Int
class RichInt    private[example] extends Int

The question is what's the difference between private modifier position in these classes declarations?

Answer 1

The first refers to the scope of the class, ie you cannot access PoorInt outside package example .

The second refers to the scope of the constructor of RichInt , which you are not providing explicitly, ie you cannot use its constructor outside package example .

For example:

// somewhere outside package example ...
val x = new RichInt // doesn't compile. Constructor is private
val y : PoorInt = ... // doesn't compile. PoorInt is not accessible from here
def f(x: PoorInt) = ... // doesn't compile. PoorInt is not accessible from here

You can also see this question .