Scala example source code file (ArrayBuffer.scala)

This example Scala source code file (ArrayBuffer.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, arraybuffer, builder, canbuildfrom, int, pararray, seqfactory, serializable, string, traversableonce

The ArrayBuffer.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 parallel.mutable.ParArray

/** An implementation of the `Buffer` class using an array to
 *  represent the assembled sequence internally. Append, update and random
 *  access take constant time (amortized time). Prepends and removes are
 *  linear in the buffer size.
 *
 *  @author  Matthias Zenger
 *  @author  Martin Odersky
 *  @version 2.8
 *  @since   1
 *  @see [[http://docs.scala-lang.org/overviews/collections/concrete-mutable-collection-classes.html#array_buffers "Scala's Collection Library overview"]]
 *  section on `Array Buffers` for more information.

 *
 *  @tparam A    the type of this arraybuffer's elements.
 *
 *  @define Coll `ArrayBuffer`
 *  @define coll arraybuffer
 *  @define thatinfo the class of the returned collection. In the standard library configuration,
 *    `That` is always `ArrayBuffer[B]` because an implicit of type `CanBuildFrom[ArrayBuffer, B, ArrayBuffer[B]]`
 *    is defined in object `ArrayBuffer`.
 *  @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 `ArrayBuffer`.
 *  @define orderDependent
 *  @define orderDependentFold
 *  @define mayNotTerminateInf
 *  @define willNotTerminateInf
 */
@SerialVersionUID(1529165946227428979L)
class ArrayBuffer[A](override protected val initialSize: Int)
  extends AbstractBuffer[A]
     with Buffer[A]
     with GenericTraversableTemplate[A, ArrayBuffer]
     with BufferLike[A, ArrayBuffer[A]]
     with IndexedSeqOptimized[A, ArrayBuffer[A]]
     with Builder[A, ArrayBuffer[A]]
     with ResizableArray[A]
     with CustomParallelizable[A, ParArray[A]]
     with Serializable {

  override def companion: GenericCompanion[ArrayBuffer] = ArrayBuffer

  import scala.collection.Traversable

  def this() = this(16)

  def clear() { reduceToSize(0) }

  override def sizeHint(len: Int) {
    if (len > size && len >= 1) {
      val newarray = new Array[AnyRef](len)
      scala.compat.Platform.arraycopy(array, 0, newarray, 0, size0)
      array = newarray
    }
  }

  override def par = ParArray.handoff[A](array.asInstanceOf[Array[A]], size)

  /** Appends a single element to this buffer and returns
   *  the identity of the buffer. It takes constant amortized time.
   *
   *  @param elem  the element to append.
   *  @return      the updated buffer.
   */
  def +=(elem: A): this.type = {
    ensureSize(size0 + 1)
    array(size0) = elem.asInstanceOf[AnyRef]
    size0 += 1
    this
  }

  /** Appends a number of elements provided by a traversable object.
   *  The identity of the buffer is returned.
   *
   *  @param xs    the traversable object.
   *  @return      the updated buffer.
   */
  override def ++=(xs: TraversableOnce[A]): this.type = xs match {
    case v: scala.collection.IndexedSeqLike[_, _] =>
      val n = v.length
      ensureSize(size0 + n)
      v.copyToArray(array.asInstanceOf[scala.Array[Any]], size0, n)
      size0 += n
      this
    case _ =>
      super.++=(xs)
  }

  /** Prepends a single element to this buffer and returns
   *  the identity of the buffer. It takes time linear in
   *  the buffer size.
   *
   *  @param elem  the element to prepend.
   *  @return      the updated buffer.
   */
  def +=:(elem: A): this.type = {
    ensureSize(size0 + 1)
    copy(0, 1, size0)
    array(0) = elem.asInstanceOf[AnyRef]
    size0 += 1
    this
  }

  /** Prepends a number of elements provided by a traversable object.
   *  The identity of the buffer is returned.
   *
   *  @param xs    the traversable object.
   *  @return      the updated buffer.
   */
  override def ++=:(xs: TraversableOnce[A]): this.type = { insertAll(0, xs.toTraversable); this }

  /** Inserts new elements at the index `n`. Opposed to method
   *  `update`, this method will not replace an element with a
   *  one. Instead, it will insert a new element at index `n`.
   *
   *  @param n     the index where a new element will be inserted.
   *  @param seq   the traversable object providing all elements to insert.
   *  @throws Predef.IndexOutOfBoundsException if `n` is out of bounds.
   */
  def insertAll(n: Int, seq: Traversable[A]) {
    if (n < 0 || n > size0) throw new IndexOutOfBoundsException(n.toString)
    val xs = seq.toList
    val len = xs.length
    ensureSize(size0 + len)
    copy(n, n + len, size0 - n)
    xs.copyToArray(array.asInstanceOf[scala.Array[Any]], n)
    size0 += len
  }

  /** Removes the element on a given index position. It takes time linear in
   *  the buffer size.
   *
   *  @param n       the index which refers to the first element to delete.
   *  @param count   the number of elements to delete
   *  @throws Predef.IndexOutOfBoundsException if `n` is out of bounds.
   */
  override def remove(n: Int, count: Int) {
    require(count >= 0, "removing negative number of elements")
    if (n < 0 || n > size0 - count) throw new IndexOutOfBoundsException(n.toString)
    copy(n + count, n, size0 - (n + count))
    reduceToSize(size0 - count)
  }

  /** Removes the element at a given index position.
   *
   *  @param n  the index which refers to the element to delete.
   *  @return   the element that was formerly at position `n`.
   */
  def remove(n: Int): A = {
    val result = apply(n)
    remove(n, 1)
    result
  }

  def result: ArrayBuffer[A] = this

  /** Defines the prefix of the string representation.
   */
  override def stringPrefix: String = "ArrayBuffer"

}

/** Factory object for the `ArrayBuffer` class.
 *
 *  $factoryInfo
 *  @define coll array buffer
 *  @define Coll `ArrayBuffer`
 */
object ArrayBuffer extends SeqFactory[ArrayBuffer] {
  /** $genericCanBuildFromInfo */
  implicit def canBuildFrom[A]: CanBuildFrom[Coll, A, ArrayBuffer[A]] = ReusableCBF.asInstanceOf[GenericCanBuildFrom[A]]
  def newBuilder[A]: Builder[A, ArrayBuffer[A]] = new ArrayBuffer[A]
}