Usages of Null / Nothing / Unit in Scala

by

You only use Nothing if the method never returns (meaning it cannot complete normally by returning, it could throw an exception). Nothing is never instantiated and is there for the benefit of the type system (to quote James Iry: “The reason Scala has a bottom type is tied to its ability to express variance in type parameters.”). From the article you linked to:

One other use of Nothing is as a return type for methods that never
return. It makes sense if you think about it. If a method’s return
type is Nothing, and there exists absolutely no instance of Nothing,
then such a method must never return.

Your logging method would return Unit. There is a value Unit so it can actually be returned. From the API docs:

Unit is a subtype of scala.AnyVal. There is only one value of type
Unit, (), and it is not represented by any object in the underlying
runtime system. A method with return type Unit is analogous to a Java
method which is declared void.

More Related Contents:

  1. Scala: Write a function to swap a number in place without using temporary variables
  2. What is a “context bound” in Scala?
  3. Understanding implicit in Scala
  4. Do scala constructor parameters default to private val?
  5. Composing Option with List in for-comprehension gives type mismatch depending on order
  6. What do all of Scala’s symbolic operators mean?
  7. NullPointerException in Scala Spark, appears to be caused be collection type?
  8. Functions vs methods in Scala
  9. What does setMaster `local[*]` mean in spark?
  10. Valid identifier characters in Scala
  11. How to find spark RDD/Dataframe size?
  12. If an Int can’t be null, what does null.asInstanceOf[Int] mean?
  13. When to use parenthesis in Scala infix notation
  14. Stream vs Views vs Iterators
  15. How to use Scala’s this typing, abstract types, etc. to implement a Self type?
  16. No configuration setting found for key ‘akka.version’
  17. Run custom task automatically before/after standard task
  18. scala – Any vs underscore in generics
  19. How to force IntelliJ IDEA to reload dependencies from build.sbt after they changed?
  20. Doing something before or after all Scalatest tests
  21. Scala : fold vs foldLeft
  22. Update operations on a Scala Case Class
  23. In scala 2 or 3, is it possible to debug implicit resolution process in runtime?
  24. How do I make a function involving futures tail recursive?
  25. How does the “scala.sys.process” from Scala 2.9 work?
  26. Difference between MutableList and ListBuffer
  27. Spark RDD default number of partitions
  28. Why does Spark RDD partition has 2GB limit for HDFS?
  29. How to sort an RDD in Scala Spark?
  30. Insert if not exists in Slick 3.0.0

Leave a Comment