write a scala method which returns Nothing

Question

-> How can we write a scala method whose return type is Nothing?

-> Do we ever need to write such methods? Are there any useful scenarios?

Answer 1

You can't actually return a value of type Nothing because there are no values of type Nothing. So the only way to define a function with return type Nothing is to never return at all.

One example would be a function that just calls itself recursively infinitely. Another would be one that always throws an exception or simply exits the application (sys.exit's return type is Nothing).

Answer 2

Actually, Nothing is used in functions which never returns or terminates abnormaly by throwing some exception eg:

scala> def funcReturnNothing : Nothing = throw new RuntimeException("runtime exception")
funcReturnNothing: Nothing

More explanation. Functions in Scala are co-variant in its return type let's say return type of the function is T so this function can only return values which are subtype of T or type of T and Nothing is subtype of all other type (Lowest in type chain) So, in actual you can not return anything useful from it but exceptions throwing has a type Nothing which you can return.