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Extending traits

Traits can also extend each other. Have a look at the following example:

trait Ping {
  def ping(): Unit = {
    System.out.println("ping")
  }
}

trait Pong {
  def pong(): Unit = {
    System.out.println("pong")
  }
}

trait PingPong extends Ping with Pong {
  def pingPong(): Unit = {
    ping()
    pong()
  }
}

object Runner extends PingPong {
  def main(args: Array[String]): Unit = {
    pingPong()
  }
}

The preceding example is simple and it should really just make the Runner object mix the two traits separately. Extending traits is useful in a design pattern called Stackable Traits, which we will be looking into later in this book.