ボス

boss.scala

class Boss {
  protected var age_ : Int = _
  def age = age_
  def age_=(value: Int): Unit = this.age_ = value
}
val tama: Boss = new Boss {
  override def age = if (20 < this.age_) 20 else this.age_
}

tama.age = 0x20
println(tama.age)

出先なのでLoad of the REPLsで動作確認した。