upper-bound

scala generics

Upper bound is used with generic types. It provides the upper bound for generic type.

For example,

trait Person:
  val name: String
 
case class Student(name: String, grade: Char) extends Person
 
def printOnConsole[T <: Person](obj: T): Unit =
  val name = obj.name
  println(s"Hello $name")
 
 
printOnConsole(Student("A", 'A'))

So, printOnConsole can only take type T which is a subtype of Person. Doing printOnConsole(A("A")) will give compilation error.