Scala Library: scala.collection.mutable.Builder
scala.collection.mutable.Builder
The base trait of all builders. A builder lets one construct a collection
incrementally, by adding elements to the builder with +=
and then converting
to the required collection type with result
.
One cannot assume that a single Builder
can build more than one instance of
the desired collection. Particular subclasses may allow such behavior.
Otherwise, result
should be treated as a terminal operation: after it is
called, no further methods should be called on the builder. Extend the
collection.mutable.ReusableBuilder trait instead of Builder
for builders that
may be reused to build multiple instances.
- Elem
- the type of elements that get added to the builder.
- To
- the type of collection that it produced.
- Source
- Since
- 2.8
Concrete Value Members From scala.collection.generic.Growable
def ++=(xs: TraversableOnce[Elem]): Builder.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*): Builder.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): Builder.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
abstract def clear(): Unit
Clears the contents of this builder. After execution of this method the builder will contain no elements.
- Definition Classes
- Builder → Growable → Clearable
(defined at 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
.
- the type of collection returned by
- 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.
- Note
- The original builder should no longer be used after
mapResult
is called.
- The original builder should no longer be used after
(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.
(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.
(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.
- a correction to add to the
(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. (defined at scala.collection.mutable.Builder)
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