Question

Given that default implementation of a Set is immutable:

val Set = immutable.Set

And in order to make it mutable one needs to import

import scala.collection.mutable.Set;

In event one needs to use both mutable and immutable Sets in a given file, how should one go about it?

Answer 1

When you need to use both mutable and immutable collections in the same file, the canonical solution is just to prefix with mutable or immutable explicitly.

import collection._

val myMutableSet: mutable.Set[Int] = mutable.Set(1, 2, 3)
val myImmutableSet: immutable.Set[Int] = immutable.Set(1, 2, 3)

AS Kim Stebel mentioned in his answer, you can also use a renaming import:

import scala.collection.mutable.{Set => MutableSet}

However mutable.Set is only one character more than MutableSet, and does not introduce any new name so you might as well just use the former form.