练习


SparkILoop.scala

package  tony.scala.sample
//importtony.scala.sample._
class  Aaa {
   override  def   toString = "I am Aaa"
}

class  SparkILoop extends Aaa with SparkILoopInit {
   override  def   toString = "I am SparkILoop"
   private[sample]  def   echo(msg: String) = {
     println(msg)
   }
}

private[sample]  trait SparkILoopInit {
   self:SparkILoop => //注释掉，看看什么效果！！！
   override  def   toString = {
     "I am SparkILoopInit"
   }
//test "Explicitly Typed Self References"
def  typeSelfReference = echo("echo works here!")
}

object  Test {
def  main(args: Array[String]) {
val  a : Aaa = new SparkILoop
val  b : SparkILoopInit = new SparkILoop
println(a)
println(b)
b.typeSelfReference
}
}
编译：
scalac SparkILoop.scala
运行：
scala tony.scala.sample.Test
注：在scala中，文件放置不用像Java一样必须按照package的目录结构。对于本例，可以把SparkILoop.scala放到任意目录下，然后运行上面的编译，执行命令。