scala.collection.mutable.MultiSet.scala Maven / Gradle / Ivy
package scala
package collection
package mutable
import java.util.concurrent.atomic.AtomicInteger
/**
* A mutable multiset.
*/
trait MultiSet[A]
extends collection.MultiSet[A]
with collection.MultiSetOps[A, MultiSet, MultiSet[A]]
with Growable[A]
with Shrinkable [A] {
override def iterableFactory: IterableFactory[MultiSet] = MultiSet
override protected def fromSpecific(coll: IterableOnce[A]): MultiSet[A] = iterableFactory.from(coll)
override protected def newSpecificBuilder: mutable.Builder[A, MultiSet[A]] = iterableFactory.newBuilder
override def empty: MultiSet[A] = iterableFactory.empty
override def knownSize: Int = super[Growable].knownSize
}
class MultiSetImpl[A] private[mutable] (elems: Map[A, AtomicInteger]) extends MultiSet[A] {
def occurrences: collection.Map[A, Int] = elems.map { case (k, v) => (k, v.get) }
def addOne(elem: A): this.type = {
elems.getOrElseUpdate(elem, new AtomicInteger).getAndIncrement
this
}
def subtractOne(elem: A): this.type = {
elems.get(elem) match {
case Some(n) => if (n.decrementAndGet <= 0) elems.subtractOne(elem)
case _ =>
}
this
}
def clear(): Unit = elems.clear()
}
object MultiSet extends IterableFactory[MultiSet] {
def from[A](source: IterableOnce[A]): MultiSet[A] = (newBuilder[A] ++= source).result()
def empty[A]: MultiSet[A] = new MultiSetImpl[A](Map.empty)
def newBuilder[A]: Builder[A, MultiSet[A]] = new GrowableBuilder[A, MultiSet[A]](empty)
}