Generic in Scala

Generic classes are classes which take a type as a parameter. They are useful for collection classes. Generic classes can be used in everyday data implementation, such as stack, queue, linked list, and so on. We will see some examples.

Defining a generic class

Generic classes take a type as a parameter within square brackets []. One 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 Stack
scala>

The preceding implementation of a Stack class takes any type A as a parameter. This means the underlying list, var elements: List[A] =...