Generics and Variance

Generics in Scala allow classes and methods to operate on types specified as parameters.

Generic Class Example

class Box[T](val value: T) {
  def get: T = value
}

Variance controls subtype relationships of parameterized types:

• +T: Covariant
• -T: Contravariant
• T: Invariant

class Covariant[+T]
class Contravariant[-T]
class Invariant[T]