TreeMap.scala

/*
import scala.collection.JavaConversions.JMapWrapperLike
import scala.collection.generic.{SortedMapFactory, CanBuildFrom}
import scala.collection

class TreeMap[A, B](implicit val ordering: Ordering[A])
  extends JMapWrapperLike[A, B, TreeMap[A, B]]
  with collection.SortedMap[A, B]
  with collection.SortedMapLike[A, B, TreeMap[A, B]] {
    
  val underlying = new java.util.TreeMap[A, B](ordering)
  override def empty: TreeMap[A, B] = TreeMap.empty
}

object TreeMap extends SortedMapFactory[TreeMap] {
  def empty[A, B](implicit ord: Ordering[A]): TreeMap[A, B] = new TreeMap[A, B]()
  implicit def canBuildFrom[A, B](implicit ord: Ordering[A]): CanBuildFrom[Coll, (A, B), TreeMap[A, B]] = new SortedMapCanBuildFrom[A, B]
}
こっちはあきらめ
*/

import scala.collection.JavaConversions.JMapWrapperLike
import scala.collection.generic.{CanBuildFrom}
import scala.collection.mutable.{Builder, MapBuilder}

class TreeMap[A, B](implicit val ordering: Ordering[A]) extends JMapWrapperLike[A, B, TreeMap[A, B]] {
  val underlying = new java.util.TreeMap[A, B](ordering)
  override def empty: TreeMap[A, B] = new TreeMap[A, B]()
  override def stringPrefix: String = "TreeMap"
}

//ほとんどSortedMapFactoryあたりからのコピー
object TreeMap {
  def apply[A, B](elems: (A, B)*)(implicit ord: Ordering[A]): TreeMap[A, B] = (newBuilder[A, B](ord) ++= elems).result

  def newBuilder[A, B](implicit ord: Ordering[A]): Builder[(A, B), TreeMap[A, B]] =
    new MapBuilder[A, B, TreeMap[A, B]](empty(ord))

  class SortedMapCanBuildFrom[A, B](implicit ord: Ordering[A]) extends CanBuildFrom[TreeMap[_, _], (A, B), TreeMap[A, B]] {
    def apply(from: TreeMap[_, _]) = newBuilder[A, B](ord)
    def apply() = newBuilder[A, B]
  }

  def empty[A, B](implicit ord: Ordering[A]): TreeMap[A, B] = new TreeMap[A, B]()
  implicit def canBuildFrom[A, B](implicit ord: Ordering[A]): CanBuildFrom[TreeMap[_, _], (A, B), TreeMap[A, B]] = new SortedMapCanBuildFrom[A, B]
}