I'm learning Scala and function programming and its immutability concept.

If my code operates on a list of objects like this:

class Devices(
  val devices_df: Dataset[Row],
){
  private lazy val _devices = _initialize_list_of_devices()

  def devices(): List[Device] = {
    _devices
  }

  private[this] def _initialize_list_of_devices(): List[Device] = {
    val devices_list = ListBuffer[Device]()
    for (device <- devices_df.collect()) {
      devices_list  = new Device(
        device.getAs[String]("DeviceName"),
      )
    }
    devices_list.toList
  }
}

And I initialize the list like this:

  val devices_list = new Devices(devices_df).devices()

And then later on, I update the objects in the list like this:

  for (device <- devices_list) {
    device.modify_instance_properties()
  }

The code works and I am able to modify the objects within the list.

However, when I try to add another object to the list with something like this:

devices_list  = new Device("append another device")

it fails whether it is val devices_list or var devices_list.

I just want to sanity check that I am not misunderstanding things and want to confirm that these are true:

• immutability does not mean the objects in the list cannot be modified
  • the objects seem to be updating their properties just fine
• immutability does mean the list cannot be changed
  • I am supposed to not be able to add another object to the list or remove an existing object from the list

Thank you for your time and help