Scala example source code file (MutableList.scala)

This example Scala source code file (MutableList.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, builder, canbuildfrom, int, iterator, linkedlist, mutablelist, nosuchelementexception, seqfactory, serializable

The MutableList.scala Scala example source code

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

package scala
package collection
package mutable

import generic._
import immutable.{List, Nil}

// !!! todo: convert to LinkedListBuffer?
/**
 *  This class is used internally to represent mutable lists. It is the
 *  basis for the implementation of the class `Queue`.
 *
 *  @author  Matthias Zenger
 *  @author  Martin Odersky
 *  @version 2.8
 *  @since   1
 *  @see [[http://docs.scala-lang.org/overviews/collections/concrete-mutable-collection-classes.html#mutable_lists "Scala's Collection Library overview"]]
 *  section on `Mutable Lists` for more information.
 */
@SerialVersionUID(5938451523372603072L)
class MutableList[A]
extends AbstractSeq[A]
   with LinearSeq[A]
   with LinearSeqOptimized[A, MutableList[A]]
   with GenericTraversableTemplate[A, MutableList]
   with Builder[A, MutableList[A]]
   with Serializable
{
  override def companion: GenericCompanion[MutableList] = MutableList

  override protected[this] def newBuilder: Builder[A, MutableList[A]] = new MutableList[A]

  protected var first0: LinkedList[A] = new LinkedList[A]
  protected var last0: LinkedList[A] = first0
  protected var len: Int = 0

  def toQueue = new Queue(first0, last0, len)

  /** Is the list empty?
   */
  override def isEmpty = len == 0

  /** Returns the first element in this list
   */
  override def head: A = if (nonEmpty) first0.head else throw new NoSuchElementException

  /** Returns the rest of this list
   */
  override def tail: MutableList[A] = {
    val tl = new MutableList[A]
    tailImpl(tl)
    tl
  }

  protected final def tailImpl(tl: MutableList[A]) {
    require(nonEmpty, "tail of empty list")
    tl.first0 = first0.tail
    tl.len = len - 1
    tl.last0 = if (tl.len == 0) tl.first0 else last0
  }

  /** Prepends a single element to this list. This operation takes constant
   *  time.
   *  @param elem  the element to prepend.
   *  @return   this $coll.
   */
  def +=: (elem: A): this.type = { prependElem(elem); this }

  /** Returns the length of this list.
   */
  override def length: Int = len

  /** Returns the `n`-th element of this list.
   *  @throws IndexOutOfBoundsException if index does not exist.
   */
  override def apply(n: Int): A = first0.apply(n)

  /** Updates the `n`-th element of this list to a new value.
   *  @throws IndexOutOfBoundsException if index does not exist.
   */
  def update(n: Int, x: A): Unit = first0.update(n, x)

  /** Returns the `n`-th element of this list or `None`
   *  if index does not exist.
   */
  def get(n: Int): Option[A] = first0.get(n)

  protected def prependElem(elem: A) {
    first0 = new LinkedList[A](elem, first0)
    if (len == 0) last0 = first0
    len = len + 1
  }

  protected def appendElem(elem: A) {
    if (len == 0) {
      prependElem(elem)
    } else {
      last0.next = new LinkedList[A]
      last0 = last0.next
      last0.elem = elem
      last0.next = new LinkedList[A] // for performance, use sentinel `object` instead?
      len = len + 1
    }
  }

  /** Returns an iterator over all elements of this list.
   */
  override def iterator: Iterator[A] = first0.iterator

  override def last = {
    if (isEmpty) throw new NoSuchElementException("MutableList.empty.last")
    last0.elem
  }

  /** Returns an instance of [[scala.List]] containing the same
   *  sequence of elements.
   */
  override def toList: List[A] = first0.toList

  /** Returns the current list of elements as a linked List
   *  sequence of elements.
   */
  private[mutable] def toLinkedList: LinkedList[A] = first0

  /** Appends a single element to this buffer. This takes constant time.
   *
   *  @param elem  the element to append.
   */
  def +=(elem: A): this.type = { appendElem(elem); this }

  def clear() {
    first0 = new LinkedList[A]
    last0 = first0
    len = 0
  }

  def result = this

  override def clone(): MutableList[A]  = {
    val bf = newBuilder
    bf ++= seq
    bf.result()
  }
}

object MutableList extends SeqFactory[MutableList] {
  implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, MutableList[A]] =
    ReusableCBF.asInstanceOf[GenericCanBuildFrom[A]]

  def newBuilder[A]: Builder[A, MutableList[A]] = new MutableList[A]
}