Scala and Spark for Big Data Analytics

Defining a generic class

Generic classes take a type as a parameter within square brackets []. One convention is to use the letter A as a type parameter identifier, though any parameter name may be used. Let's see a minimal example on Scala REPL, as follows:

scala> class Stack[A] {     |       private var elements: List[A] = Nil     |       def push(x: A) { elements = x :: elements }     |       def peek: A = elements.head     |       def pop(): A = {     |         val currentTop = peek     |         elements = elements.tail     |         currentTop     |       }     |     }defined class Stackscala>

The preceding implementation of a Stack class takes any type A as a parameter. This means the underlying list, var elements: List[A] = Nil can only store elements of type A. The procedure def push only accepts objects of type A (note: ...