Traits and Mixins

Code

trait Logger {
  def log(msg: String): Unit = println(s"[LOG] $msg")
}

trait TimestampedLogger extends Logger {
  override def log(msg: String): Unit =
    super.log(s"${System.currentTimeMillis()} - $msg")
}

class Service extends TimestampedLogger {
  def run(): Unit = log("Service started")
}

// Linearization: Service -> TimestampedLogger -> Logger
new Service().run()
// [LOG] 1700000000000 - Service started

Explanation

Traits are Scala's interface with optional implementations. Multiple traits can be mixed in (stackable modification), and the linearization order determines how super calls resolve. This enables flexible composition without deep inheritance hierarchies.

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