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Scala example source code file (LinkedHashMap.scala)

This example Scala source code file (LinkedHashMap.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, entry, entry, hashtable, iterator, iterator, linkedentry, linkedhashmap, maplike, none, option

The Scala LinkedHashMap.scala source code

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



package scala.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 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 = findEntry(key)
    if (e == null) { 
      val e = new Entry(key, value)
      addEntry(e)
      updateLinkedEntries(e)
      None 
    } else { 
      val v = e.value
      e.value = value
      Some(v) 
    }
  }

  private def updateLinkedEntries(e: Entry) {
    if (firstEntry == null) firstEntry = e
    else { lastEntry.later = e; e.earlier = lastEntry }
    lastEntry = e
  }

  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)
    }
  }

  def += (kv: (A, B)): this.type = { put(kv._1, kv._2); this }
  def -=(key: A): this.type = { remove(key); this }

  def iterator: Iterator[(A, B)] = new Iterator[(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
  }

  override def keysIterator: Iterator[A] = new Iterator[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 Iterator[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
    }
  }

  override def clear() {
    clearTable()
    firstEntry = null
  }
  
  private def writeObject(out: java.io.ObjectOutputStream) {
    serializeTo(out, _.value)
  }
  
  private def readObject(in: java.io.ObjectInputStream) {
    firstEntry = null
    lastEntry = null
    init[B](in, { (key, value) =>
      val entry = new Entry(key, value)
      updateLinkedEntries(entry)
      entry
    })
  }
}

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