scala.collection.mutable.ReusableBuilder

trait ReusableBuilder[-Elem, +To] extends Builder[Elem, To]

ReusableBuilder is a marker trait that indicates that a Builder can be reused to build more than one instance of a collection. In particular, calling result followed by clear will produce a collection and reset the builder to begin building a new collection of the same type.

It is up to subclasses to implement this behavior, and to document any other behavior that varies from standard ReusableBuilder usage (e.g. operations being well-defined after a call to result , or allowing multiple calls to result to obtain different snapshots of a collection under construction).

Concrete Value Members From scala.collection.generic.Growable

def ++=(xs: TraversableOnce[Elem]): ReusableBuilder.this.type

adds all elements produced by a TraversableOnce to this growable collection.

  • xs
    • the TraversableOnce producing the elements to add.
  • returns
    • the growable collection itself.
  • Definition Classes
    • Growable

(defined at scala.collection.generic.Growable)

def +=(elem1: Elem, elem2: Elem, elems: Elem*): ReusableBuilder.this.type

adds two or more elements to this growable collection.

  • elem1
    • the first element to add.
  • elem2
    • the second element to add.
  • elems
    • the remaining elements to add.
  • returns
    • the growable collection itself
  • Definition Classes
    • Growable

(defined at scala.collection.generic.Growable)

Abstract Value Members From scala.collection.mutable.Builder

abstract def +=(elem: Elem): ReusableBuilder.this.type

Adds a single element to the builder.

  • elem
    • the element to be added.
  • returns
    • the builder itself.
  • Definition Classes
    • Builder → Growable

(defined at scala.collection.mutable.Builder)

Concrete Value Members From scala.collection.mutable.Builder

def mapResult[NewTo](f: (To) ⇒ NewTo): Builder[Elem, NewTo]

Creates a new builder by applying a transformation function to the results of this builder.

  • NewTo
    • the type of collection returned by f .
  • f
    • the transformation function.
  • returns
    • a new builder which is the same as the current builder except that a transformation function is applied to this builder’s result.
  • Definition Classes
    • Builder
  • Note
    • The original builder should no longer be used after mapResult is called.

(defined at scala.collection.mutable.Builder)

def sizeHint(size: Int): Unit

Gives a hint how many elements are expected to be added when the next result is called. Some builder classes will optimize their representation based on the hint. However, builder implementations are still required to work correctly even if the hint is wrong, i.e. a different number of elements is added.

  • size
    • the hint how many elements will be added.
  • Definition Classes
    • Builder

(defined at scala.collection.mutable.Builder)

def sizeHint(coll: TraversableLike[_, _]): Unit

Gives a hint that one expects the result of this builder to have the same size as the given collection, plus some delta. This will provide a hint only if the collection is known to have a cheap size method. Currently this is assumed to be the case if and only if the collection is of type IndexedSeqLike . Some builder classes will optimize their representation based on the hint. However, builder implementations are still required to work correctly even if the hint is wrong, i.e. a different number of elements is added.

  • coll
    • the collection which serves as a hint for the result’s size.
  • Definition Classes
    • Builder

(defined at scala.collection.mutable.Builder)

def sizeHint(coll: TraversableLike[_, _], delta: Int): Unit

Gives a hint that one expects the result of this builder to have the same size as the given collection, plus some delta. This will provide a hint only if the collection is known to have a cheap size method. Currently this is assumed to be the case if and only if the collection is of type IndexedSeqLike . Some builder classes will optimize their representation based on the hint. However, builder implementations are still required to work correctly even if the hint is wrong, i.e. a different number of elements is added.

  • coll
    • the collection which serves as a hint for the result’s size.
  • delta
    • a correction to add to the coll.size to produce the size hint.
  • Definition Classes
    • Builder

(defined at scala.collection.mutable.Builder)

def sizeHintBounded(size: Int, boundingColl: TraversableLike[_, _]): Unit

Gives a hint how many elements are expected to be added when the next result is called, together with an upper bound given by the size of some other collection. Some builder classes will optimize their representation based on the hint. However, builder implementations are still required to work correctly even if the hint is wrong, i.e. a different number of elements is added.

  • size
    • the hint how many elements will be added.
  • boundingColl
    • the bounding collection. If it is an IndexedSeqLike, then sizes larger than collection’s size are reduced.
  • Definition Classes
    • Builder

(defined at scala.collection.mutable.Builder)

Concrete Value Members From scala.collection.mutable.ReusableBuilder

abstract def clear(): Unit

Clears the contents of this builder. After execution of this method, the builder will contain no elements.

If executed immediately after a call to result , this allows a new instance of the same type of collection to be built.

  • Definition Classes
    • ReusableBuilder → Builder → Growable → Clearable (defined at scala.collection.mutable.ReusableBuilder)

Full Source:

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2016, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */


package scala
package collection
package mutable

import generic._

/** `ReusableBuilder` is a marker trait that indicates that a `Builder`
 *  can be reused to build more than one instance of a collection.  In
 *  particular, calling `result` followed by `clear` will produce a
 *  collection and reset the builder to begin building a new collection
 *  of the same type.
 *
 *  It is up to subclasses to implement this behavior, and to document any
 *  other behavior that varies from standard `ReusableBuilder` usage
 *  (e.g. operations being well-defined after a call to `result`, or allowing
 *  multiple calls to result to obtain different snapshots of a collection under
 *  construction).
 *
 *  @tparam  Elem  the type of elements that get added to the builder.
 *  @tparam  To    the type of collection that it produced.
 *
 *  @since 2.12
 */
trait ReusableBuilder[-Elem, +To] extends Builder[Elem, To] {
  /** Clears the contents of this builder.
   *  After execution of this method, the builder will contain no elements.
   *
   *  If executed immediately after a call to `result`, this allows a new
   *  instance of the same type of collection to be built.
   */
  override def clear(): Unit    // Note: overriding for scaladoc only!

  /** Produces a collection from the added elements.
   *
   *  After a call to `result`, the behavior of all other methods is undefined
   *  save for `clear`.  If `clear` is called, then the builder is reset and
   *  may be used to build another instance.
   *  
   *  @return a collection containing the elements added to this builder.
   */
  override def result(): To    // Note: overriding for scaladoc only!
}