Scala模拟表查询例子

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package testtrait PartitionStrategy extends Serializable {  /** Returns the partition number for a given edge. */  def getPartition(key: Int): Int  def loadMetisFile()}object PartitionStrategy {    def fromString(s: String): PartitionStrategy = s match {    case "MetisPartition" => MetisPartition    case _ => throw new IllegalArgumentException("Invalid PartitionStrategy: " + s)  }         case object MetisPartition extends PartitionStrategy {      val metisMap =new scala.collection.mutable.HashMap[Int,Int]             def loadMetisFile() {        mockLoadFile()       }            def mockLoadFile() {      try {       var id = 1 ;       while(id < 10000)       {           var partition = 5 ;           metisMap.put(id, partition)           id = id +1        }       println("size: " + metisMap.size)    } catch  {       case ex: Exception => { // Handle missing file             ex.printStackTrace()       }      }  }         override def getPartition(src: Int): Int = {      var s = metisMap.get(src)      if(!s.isEmpty)      return s.getOrElse(0)      else        throw new IllegalArgumentException("Metis can't find partition!")    }  }}

package testobject TestPartition2 {       def main(args :Array[String]){     try {        val partitionStrategy = PartitionStrategy.fromString("MetisPartition")         partitionStrategy.loadMetisFile          println(partitionStrategy.getPartition(555))//     println(MetisPartitioner.getMetisPartition(1))     } catch {         case ex: Exception => {           ex.printStackTrace()          }     }    }

总结：trait有人说像接口，但我觉得更像抽象类，此外，参考这个文档：

http://blog.csdn.net/wangxiaotongfan/article/details/48242029

注意几点：

注意：object不能提供构造器参数，也就是说object必须是无参的

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