scala 自定义实现枚举

java使用枚举类型，所以不用
scala但是没有枚举类型，如果项目中 需要 用到枚举或者类似枚举 。scala 就需要 使用其他方式来实现。
基本来说 有三种
第一种 ，就是在项目中单独写一个java文件，在文件中声明 枚举类型，然后在其他scala文件中去引入 这个java文件类 ，就可以达到 使用枚举类型的方法

第二种 ，就是使用 case 类来达到当做枚举类型的使用，可以参考
https://github.com/ktonga/tweet-virality/blob/12fe9e789234b95a1a337ee887d90e5a021fca92/app/com/github/ktonga/tweetvirality/models/twitter/Neo4j.scala

 case class NeoLabel(name: String) extends Label
  case class NeoRelType(name: String) extends RelationshipType

  val User = NeoLabel("User")
  val Tweet = NeoLabel("Tweet")

  val Follows = NeoRelType("Follows")
  val FollowedBy = NeoRelType("FollowedBy")
  val Twitted = NeoRelType("Twitted")
  val TwittedBy = NeoRelType("TwittedBy")

在调用的时候

 NeoLabel.User
NeoLabel.Tweet

第三种使用 封闭的trait 来实现

 class enum extends scala.annotation.StaticAnnotation;

@enum sealed trait AggregateOp extends scala.Product with scala.Serializable {
    def json: String
  };
  object AggregateOpEnums {
    case object Values extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"values\""
    };
    case object Count extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"count\""
    };
    case object Valid extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"valid\""
    };
    case object Missing extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"missing\""
    };
    case object Distinct extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"distinct\""
    };
    case object Sum extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"sum\""
    };
    case object Mean extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"mean\""
    };
    case object Average extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"average\""
    };
    case object Variance extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"variance\""
    };
    case object Variancep extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"variancep\""
    };
    case object Stdev extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"stdev\""
    };
    case object Stdevp extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"stdevp\""
    };
    case object Median extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"median\""
    };
    case object Q1 extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"q1\""
    };
    case object Q3 extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"q3\""
    };
    case object Modeskew extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"modeskew\""
    };
    case object Min extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"min\""
    };
    case object Max extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"max\""
    };
    case object Argmin extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"argmin\""
    };
    case object Argmax extends AggregateOp with scala.Product with scala.Serializable {
      val json: String = "\"argmax\""
    }
  };