what are the types Unit? [closed]

Answer 1

• Unit - essentially a type that has only one value, () - it is used in places where you would normally use void in Java.
• Null - another type that has only one value, null. It is a subtype of all reference (nullable) types.
• Nothing - a type that has no values and is a subtype of all other types. The only valid expression that has type Nothing is an expression that always throws an exception. Nothing is useful to represent things like for example, an empty list, which has a type List[Nothing]. Thanks to that, it can be used everywhere where a List[E] is required, regardless of type E (this is also powered by list's covariance).