Scala example source code file (LinkedHashMap.scala)

This example Scala source code file (LinkedHashMap.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

a, abstractiterator, b, c, entry, iterator, linkedhashmap, none, option, u

The LinkedHashMap.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */



package scala
package collection
package mutable

import generic._

/** $factoryInfo
 *  @define Coll `LinkedHashMap`
 *  @define coll linked hash map
 */
object LinkedHashMap extends MutableMapFactory[LinkedHashMap] {
  implicit def canBuildFrom[A, B]: CanBuildFrom[Coll, (A, B), LinkedHashMap[A, B]] = new MapCanBuildFrom[A, B]
  def empty[A, B] = new LinkedHashMap[A, B]
}

/** This class implements mutable maps using a hashtable.
 *  The iterator and all traversal methods of this class visit elements in the order they were inserted.
 *
 *  @tparam A    the type of the keys contained in this hash map.
 *  @tparam B    the type of the values assigned to keys in this hash map.
 *
 *  @define Coll `LinkedHashMap`
 *  @define coll linked hash map
 *  @define thatinfo the class of the returned collection. In the standard library configuration,
 *    `That` is always `LinkedHashMap[A, B]` if the elements contained in the resulting collection are
 *    pairs of type `(A, B)`. This is because an implicit of type `CanBuildFrom[LinkedHashMap, (A, B), LinkedHashMap[A, B]]`
 *    is defined in object `LinkedHashMap`. 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 `LinkedHashMap`.
 *  @define mayNotTerminateInf
 *  @define willNotTerminateInf
 *  @define orderDependent
 *  @define orderDependentFold
 */
@SerialVersionUID(1L)
class LinkedHashMap[A, B] extends AbstractMap[A, B]
                             with Map[A, B]
                             with MapLike[A, B, LinkedHashMap[A, B]]
                             with HashTable[A, LinkedEntry[A, B]]
                             with Serializable
{

  override def empty = LinkedHashMap.empty[A, B]
  override def size = tableSize

  type Entry = LinkedEntry[A, B]

  @transient protected var firstEntry: Entry = null
  @transient protected var lastEntry: Entry = null

  def get(key: A): Option[B] = {
    val e = findEntry(key)
    if (e == null) None
    else Some(e.value)
  }

  override def put(key: A, value: B): Option[B] = {
    val e = findOrAddEntry(key, value)
    if (e eq null) None
    else { val v = e.value; e.value = value; Some(v) }
  }

  override def remove(key: A): Option[B] = {
    val e = removeEntry(key)
    if (e eq null) None
    else {
      if (e.earlier eq null) firstEntry = e.later
      else e.earlier.later = e.later
      if (e.later eq null) lastEntry = e.earlier
      else e.later.earlier = e.earlier
      Some(e.value)
    }
  }

  @deprecatedOverriding("+= should not be overridden so it stays consistent with put.", "2.11.0")
  def += (kv: (A, B)): this.type = { put(kv._1, kv._2); this }

  @deprecatedOverriding("-= should not be overridden so it stays consistent with remove.", "2.11.0")
  def -=(key: A): this.type = { remove(key); this }

  def iterator: Iterator[(A, B)] = new AbstractIterator[(A, B)] {
    private var cur = firstEntry
    def hasNext = cur ne null
    def next =
      if (hasNext) { val res = (cur.key, cur.value); cur = cur.later; res }
      else Iterator.empty.next()
  }

  protected class FilteredKeys(p: A => Boolean) extends super.FilteredKeys(p) {
    override def empty = LinkedHashMap.empty
  }

  override def filterKeys(p: A => Boolean): scala.collection.Map[A, B] = new FilteredKeys(p)

  protected class MappedValues[C](f: B => C) extends super.MappedValues[C](f) {
    override def empty = LinkedHashMap.empty
  }

  override def mapValues[C](f: B => C): scala.collection.Map[A, C] = new MappedValues(f)

  protected class DefaultKeySet extends super.DefaultKeySet {
    override def empty = LinkedHashSet.empty
  }

  override def keySet: scala.collection.Set[A] = new DefaultKeySet

  override def keysIterator: Iterator[A] = new AbstractIterator[A] {
    private var cur = firstEntry
    def hasNext = cur ne null
    def next =
      if (hasNext) { val res = cur.key; cur = cur.later; res }
      else Iterator.empty.next()
  }

  override def valuesIterator: Iterator[B] = new AbstractIterator[B] {
    private var cur = firstEntry
    def hasNext = cur ne null
    def next =
      if (hasNext) { val res = cur.value; cur = cur.later; res }
      else Iterator.empty.next()
  }

  override def foreach[U](f: ((A, B)) => U) {
    var cur = firstEntry
    while (cur ne null) {
      f((cur.key, cur.value))
      cur = cur.later
    }
  }

  protected override def foreachEntry[U](f: Entry => U) {
    var cur = firstEntry
    while (cur ne null) {
      f(cur)
      cur = cur.later
    }
  }

  protected def createNewEntry[B1](key: A, value: B1): Entry = {
    val e = new Entry(key, value.asInstanceOf[B])
    if (firstEntry eq null) firstEntry = e
    else { lastEntry.later = e; e.earlier = lastEntry }
    lastEntry = e
    e
  }

  override def clear() {
    clearTable()
    firstEntry = null
  }

  private def writeObject(out: java.io.ObjectOutputStream) {
    serializeTo(out, { entry =>
      out.writeObject(entry.key)
      out.writeObject(entry.value)
    })
  }

  private def readObject(in: java.io.ObjectInputStream) {
    firstEntry = null
    lastEntry = null
    init(in, createNewEntry(in.readObject().asInstanceOf[A], in.readObject()))
  }
}