Try to have a case class pooling

case-class-pool.scala

abstract case class Toto private[Toto] (i: Int, j: String) {
  val hashCodeVal : Int
  override def hashCode() : Int = hashCodeVal
  def copy(i: Int = i, j: String = j) = {
    Toto(i,j)
  }
}

object Toto {
  val totoPool = scala.collection.mutable.WeakHashMap[Int, Toto]()
  def apply(i: Int, j: String): Toto = {
    val hash = hashCode(i,j)
    println(totoPool)
    totoPool.getOrElseUpdate(hash, new Toto(i: Int, j: String) {
      override val hashCodeVal : Int = hash
    })
  }

  def hashCode(i: Int, j: String) : Int = {
    (i,j).hashCode()
  }
}