Single Abstract Method (SAM)

Introduced in Scala 2.12. If a trait or abstract class has exactly one abstract method, then it can be presented as a function literal:

trait Printable {

  // Exactly one abstract method
  def print(message: String): Unit

  // optional fields
  val name = "Printable Object"

}

// Object-oriented syntax
new Printable {
    def print(message: String): Unit = println(message)
}
// res0: Printable = $anon$1@1e91fe2f

// SAM syntax
val prn: Printable = (msg: String) => println(msg)
// prn: Printable = $anonfun$1@3de800ce