in scala
class Null

`final abstract class` Null
  `extends` java.lang.Object

  Class `Null` (previously named `AllRef` in Scala 2.2.0 and older versions) is - together with class `Nothing` - at the bottom of the Scala type hierarchy.

  Type `Null` is a subtype of all reference types; its only instance is the `null` reference. Since `Null` is not a subtype of value types, `null` is not a member of any such type. For instance, it is not possible to assign `null` to a variable of type `Int`.