create a new class and a few example values

Example3a.scala

case class ScalaBean[A](initA: A):
  private var theA: A = initA
  def getTheA: A = theA
  def setTheA(a: A): Unit = {
    this.theA = a
  }

val bean1: ScalaBean[Int] = ScalaBean(1)
val bean2: ScalaBean[String] = ScalaBean("Foo")
val bean3: ScalaBean[Int] = ScalaBean(2)

// val beanList1: List[ScalaBean[Any]] = List(bean1, bean2, bean3)
val beanList2: List[ScalaBean[?]] = List(bean1, bean2, bean3)
val beanList3: List[ScalaBean[Int]] = List(bean1, bean3)