Generics

scala> List(1,2,3,4)
val res0: List[Int] = List(1, 2, 3, 4)

scala> val optX = Option(3)
val optX: Option[Int] = Some(3)

case class Pair[A](first: A, second: A)
// defined case class Pair
                                                                                
scala> val intPair = Pair[Int](3, 4)
val intPair: Pair[Int] = Pair(3,4)
                                                                                
scala> val doublePair = Pair[Double](1.1, 3.14)
val doublePair: Pair[Double] = Pair(1.1,3.14)

Defining Generic Classes and Traits

In Scala, you can define generic classes and traits using square brackets to specify type parameters.

class Box[T] {
  private var content: Option[T] = None
  
  def put(item: T): Unit = {
    content = Some(item)
  }

  def get(): Option[T] = content
}

trait Comparable[T] {
  def compareTo(other: T): Int
}

Using Generic Classes

val intBox = new Box[Int]
intBox.put(123)

val stringBox = new Box[String]
stringBox.put("Hello Generics")

println(intBox.get())  // Outputs: Some(123)
println(stringBox.get())  // Outputs: Some("Hello Generics")

Defining and Using Generic Methods

Scala allows defining methods with their own type parameters, which can be useful for utility methods.

object Utils {
  def getFirstElement[T](list: List[T]): Option[T] = list.headOption
}

val numbers = List(1, 2, 3)
val names = List("Alice", "Bob", "Charlie")

println(Utils.getFirstElement(numbers))  // Outputs: Some(1)
println(Utils.getFirstElement(names))  // Outputs: Some("Alice")