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Scala example source code file (ListMap.scala)

This example Scala source code file (ListMap.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Scala tags/keywords

a, a, b, b, canbuildfrom, int, list, list, listmap, listmap, map, maplike, option, serializable

The Scala ListMap.scala source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2011, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */



package scala.collection
package mutable

import generic._

/** A simple mutable map backed by a list.
 * 
 *  @tparam A    the type of the keys contained in this list map.
 *  @tparam B    the type of the values assigned to keys in this list map.
 *  
 *  @define Coll mutable.ListMap
 *  @define coll mutable list map
 *  @define thatinfo the class of the returned collection. In the standard library configuration,
 *    `That` is always `ListMap[A, B]` if the elements contained in the resulting collection are 
 *    pairs of type `(A, B)`. This is because an implicit of type `CanBuildFrom[ListMap, (A, B), ListMap[A, B]]`
 *    is defined in object `ListMap`. Otherwise, `That` resolves to the most specific type that doesn't have
 *    to contain pairs of type `(A, B)`, which is `Iterable`.
 *  @define bfinfo an implicit value of class `CanBuildFrom` which determines the
 *    result class `That` from the current representation type `Repr`
 *    and the new element type `B`. This is usually the `canBuildFrom` value
 *    defined in object `ListMap`.
 *  @define mayNotTerminateInf
 *  @define willNotTerminateInf
 *  @define orderDependent
 *  @define orderDependentFold
 */
class ListMap[A, B] extends Map[A, B] with MapLike[A, B, ListMap[A, B]] with Serializable {

  
  override def empty = ListMap.empty[A, B]

  private var elems: List[(A, B)] = List()
  private var siz: Int = 0

  def get(key: A): Option[B] = elems find (_._1 == key) map (_._2)
  def iterator: Iterator[(A, B)] = elems.iterator
  def += (kv: (A, B)) = { elems = remove(kv._1, elems); elems = kv :: elems; siz += 1; this }
  def -= (key: A) = { elems = remove(key, elems); this }

  private def remove(key: A, elems: List[(A, B)]): List[(A, B)] = 
    if (elems.isEmpty) elems
    else if (elems.head._1 == key) { siz -= 1; elems.tail }
    else elems.head :: remove(key, elems.tail)
  
  override def clear() = { elems = List(); siz = 0 }
  override def size: Int = siz
}

/** $factoryInfo
 *  @define Coll mutable.ListMap
 *  @define coll mutable list map
 */
object ListMap extends MutableMapFactory[ListMap] {
  implicit def canBuildFrom[A, B]: CanBuildFrom[Coll, (A, B), ListMap[A, B]] = new MapCanBuildFrom[A, B]
  def empty[A, B]: ListMap[A, B] = new ListMap[A, B]
}

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