ScalaSchool

Anonymous Classes

An anonymous class is a synthetic subsclass generated by the Scala compiler from a new expression in which the class or trait name is followed by curly braces. The curly braces contains the body of the anonymous subclass, which may be empty. However, if the name following refers to a trait or class that contains abstract members, these must be made concrete inside the curly braces that define the body of the anonymous subsclass.

trait RationalTrait {
  val numerArg: Int
  val denomArg: Int
} 

val anonymousClass = new RationalTrait {
    val numerArg = 1
    val denomArg = 2
}

Anonymous Classes

Lambda Expressions and “SAM” types

In Java 8, a lambda expression can be used anywhere an instance of a class or interface that contains a single abstract method (SAM) is required.

// This trait (could also be an abstract class) has a single abstract method
trait HasGrade {
  def getGrade(): String
}

//  this function literal can be used anywhere an instance of HasGrade it required
val reportGrade = () => "A"