When to use 'Nothing'...

scala> //One of the usage of Nothing is with

scala> //abnormal program termination #253

scala>

scala> ///////////////////////////////////

scala> //  An Example WITHOUT Nothing

scala> ///////////////////////////////////

scala> def error(msg:String): Unit = {
     |   println("Message.. is -> " + msg)
     |   throw new RuntimeException(msg)
     | }
error: (msg: String)Unit

scala>

scala> def isValidNo(no: Int):Boolean = {
     |   if(no == 0) {
     |     error("Invalid no")
     |   }else {
     |     true
     |   }
     | }
<console>:45: error: type mismatch;
 found   : Unit
 required: Boolean
           error("Invalid no")
                ^

scala>

scala> ///////////////////////////////////

scala> //  An Example WITH Nothing

scala> ///////////////////////////////////

scala> def error(msg:String): Nothing = {
     |   println("Message.. is -> " + msg)
     |   throw new RuntimeException(msg)
     | }
error: (msg: String)Nothing

scala>

scala> def isValidNo(no: Int):Boolean = {
     |   if(no == 0) {
     |     error("Invalid no")
     |   }else {
     |     true
     |   }
     | }
isValidNo: (no: Int)Boolean

Scala Class Hierarchy...

1. Any #247
1. Available Methods #246
1. ==
2. !=
3. equals
4. ##
5. hashCode
6. toString
2. AnyVal (Value Class)
1. All primitive types falls under this category
2. It is also possible to create our own AnyVal types #254
3. ----------------
4. Double
5. Float
6. Long
7. Int
1. RichInt(Booster Class) ; Contains Implicit conversion methods...#249
8. Short
9. Byte
10. Char 
11. Boolean
12. Unit
1. Is represented by () #247
2. Is equivalent to Void
13. ...
14. ----------------
3. AnyRef (Reference Classes) (Is the equivalent of Object in Java) #250
1. String
2. Iterable
3. Seq
4. List
5. ...
6. ----------------
7. Useful Methods
8. ----------------
9. ==  #252
10. eq
2. Bottom Classes
1. Null
1. Is a subclass of every other Reference Classes
2. Used for null reference #252
2. Nothing
1. Is a subclass of every other class
2. Can be used to signal abnormal termination etc... #253