Scala “encourages” using immutable collections (hence they are those used by default) however sometimes mutable collections might have some benefits, either for CPU / memory performance, for code readability or simply a matter of preference. As we saw earlier, Scala provides concrete mutable collections in scala.collections.mutable

• Best practice suggests that you prefix mutable collections with mutable, this might not seem useful for ArrayBuffer, but it will for scala.collections.mutable.Map
• ArrayBuffer is the more or less equivalent to java’s java.util.ArrayList which is backed by an array
• ListBuffer is the mutable partner for scala’s immutable List, implemented as a Linked List
• There are many other mutable collections types, see links below for more information

See Also opens in new page

• Concrete Mutable Collection Classes
• What is scala's equivalent of java.util.ArrayList in stackoverflow
• scala.collections.mutable package docs