Some(ArrayBuffer("myString", "String")).toList.flatten
First turn the Option[ArrayBuffer[String]] into a List[ArrayBuffer[String]]. Then flatten the List[ArrayBuffer[String]] into a List[String]
Scala Documentation
docs.scala-lang.org › overviews › scala-book › arraybuffer-examples.html
The ArrayBuffer Class | Scala Book | Scala Documentation
scala> import scala.collection.mutable.ArrayBuffer scala> val nums = ArrayBuffer(1, 2, 3) val nums: ArrayBuffer[Int] = ArrayBuffer(1, 2, 3) scala> nums += 4 val res0: ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4) scala> nums += 5 += 6 val res1: ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, 6) scala> nums ++= List(7, 8, 9) val res2: ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, 6, 7, 8, 9) scala> nums -= 9 val res3: ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, 6, 7, 8) scala> nums -= 7 -= 8 val res4: ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, 6) scala> nums --= Array(5, 6) val res5: ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4)
TutorialsPoint
tutorialspoint.com › scala_collections › scala_collections_arraybuffer.htm
Scala Collections - ArrayBuffer
In case underlying array is full then a new larger array is created and all elements are copied to larger array. The following is the syntax for declaring an ArrayBuffer variable. ... Here, z is declared as an array-buffer of Strings which is initially empty. Values can be added by using commands like the following − ... import scala.collection.mutable.ArrayBuffer object Demo { def main(args: Array[String]) = { var myList = ArrayBuffer("Zara","Nuha","Ayan") println(myList); // Add an element myList += "Welcome"; // Add two element myList += ("To", "Tutorialspoint"); println(myList); // Remove an element myList -= "Welcome"; // print second element println(myList(1)); } }
Baeldung
baeldung.com › home › scala collections › guide to arraybuffer
Guide to ArrayBuffer | Baeldung on Scala
March 18, 2024 - For immutable lists, a new list is always created if we try to append another element. Another important detail is that the ArrayBuffer implementation in specific is backed up by an indexed array, meaning that we have constant access to any element of the collection. ... scala> import scala.collection.mutable.ArrayBuffer scala> val nums = ArrayBuffer(1, 2, 3) val nums: ArrayBuffer[Int] = ArrayBuffer(1, 2, 3)
Scala Programming Language
scala-lang.org › api › current › scala › collection › mutable › ArrayBuffer.html
ArrayBuffer
the iterable object containing the elements to append. Returns · this buffer · Inherited from: Buffer · Source · Buffer.scala · override def appended[B >: A](elem: B): ArrayBuffer[B] A copy of this sequence with an element appended. A copy of this sequence with an element appended. Note: will not terminate for infinite-sized collections. Example: scala> val a = List(1) a: List[Int] = List(1) scala> val b = a :+ 2 b: List[Int] = List(1, 2) scala> println(a) List(1) B ·
Scala Programming Language
scala-lang.org › api › 2.13.3 › scala › collection › mutable › ArrayBuffer.html
Scala Standard Library 2.13.3 - scala.collection.mutable.ArrayBuffer
In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type. ... Tests whether this iterable collection can be repeatedly traversed. Tests whether this iterable collection can be repeatedly traversed. Always true for Iterables and false for Iterators unless overridden. ... The companion object of this array buffer, providing various factory methods. The companion object of this array buffer, providing various factory methods. ... ArrayBuffer → IndexedBuffer → IndexedSeq → IndexedSeq → Buffer → Seq → Iterable → Seq → Iterable → IterableOps
GeeksforGeeks
geeksforgeeks.org › scala › scala-arraybuffer
Scala | ArrayBuffer - GeeksforGeeks
March 5, 2019 - Array in scala is homogeneous and mutable, i.e it contains elements of the same data type and its elements can change but the size of array size can’t change. To create a mutable, indexed sequence whose size can change ArrayBuffer class is used. To use, ArrayBuffer, scala.collection.mutable.ArrayBuffer class is imported, an instance of ArrayBuffer is created.
Top answer 1 of 3
3
Some(ArrayBuffer("myString", "String")).toList.flatten
First turn the Option[ArrayBuffer[String]] into a List[ArrayBuffer[String]]. Then flatten the List[ArrayBuffer[String]] into a List[String]
2 of 3
1
You can map it further:
Some(ArrayBuffer("myString", "String"))
.map(_.toList)
.get
Instead of get you can use orElse to provide a default value and avoid exception thrown.
Alvin Alexander
alvinalexander.com › scala › arraybuffer-class-methods-syntax-examples-reference
Scala ArrayBuffer class: methods, syntax, and examples | alvinalexander.com
Use the ArrayBuffer class when you want to use a general-purpose, mutable indexed sequence in your Scala applications: Mutable: you can change the elements in the collection, and resize the collection · Indexed: random access of elements is very fast; this means you can access elements quickly by their element number, such as people(12345432) (a linked list would be very slow for this purpose)
Artima
booksites.artima.com › programming_in_scala_2ed › examples › html › ch17.html
Code Examples for Programming in Scala, Second Edition
scala> import scala.collection.mutable.ListBuffer import scala.collection.mutable.ListBuffer scala> val buf = new ListBuffer[Int] buf: scala.collection.mutable.ListBuffer[Int] = ListBuffer() scala> buf += 1 res4: buf.type = ListBuffer(1) scala> buf += 2 res5: buf.type = ListBuffer(1, 2) scala> buf res6: scala.collection.mutable.ListBuffer[Int] = ListBuffer(1, 2) scala> 3 +=: buf res7: buf.type = ListBuffer(3, 1, 2) scala> buf.toList res8: List[Int] = List(3, 1, 2) scala> import scala.collection.mutable.ArrayBuffer import scala.collection.mutable.ArrayBuffer ·
Scala Documentation
docs.scala-lang.org › overviews › collections-2.13 › concrete-mutable-collection-classes.html
Concrete Mutable Collection Classes | Collections | Scala Documentation
scala> val buf = scala.collect... buf.toArray res34: Array[Int] = Array(1, 10) A ListBuffer is like an array buffer except that it uses a linked list internally instead of an array....
Top answer 1 of 4
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There's a generic method to that can convert between arbitrary collection types.
Array(1, 2, 3).to[ArrayBuffer]
Or from Scala 2.13 onwards:
Array(1, 2, 3).to(ArrayBuffer)
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Use Iterable: _*:
val arr = Array(1,2,3)
arr: Array[Int] = Array(1, 2, 3)
val buf = collection.mutable.ArrayBuffer(arr: _*)
buf: scala.collection.mutable.ArrayBuffer[Int] = ArrayBuffer(1, 2, 3)
The _* means to unpack the Iterable elements. So arr: _* unpacks the elements of arr into a variable length list - which is an acceptable parameter list for `ArrayBuffer.
Scala Documentation
docs.scala-lang.org › overviews › collections › concrete-mutable-collection-classes.html
Concrete Mutable Collection Classes | Collections (Scala 2.8 - 2.12) | Scala Documentation
scala> val buf = scala.collect... buf.toArray res34: Array[Int] = Array(1, 10) A ListBuffer is like an array buffer except that it uses a linked list internally instead of an array....
Alvin Alexander
alvinalexander.com › scala › make-arraybuffer-class-default-mutable-indexed-sequence-scala-cookbook
Make the ArrayBuffer class your default mutable indexed sequence (Scala best practice) | alvinalexander.com
July 12, 2021 - The Scala documentation on the ListBuffer states, “A ListBuffer is like an array buffer except that it uses a linked list internally instead of an array. If you plan to convert the buffer to a list once it is built up, use a list buffer instead of an array buffer.”
Scala Programming Language
scala-lang.org › api › 2.12.x › scala › collection › mutable › ArrayBuffer.html
Scala Standard Library 2.12.20 - scala.collection.mutable.ArrayBuffer
December 2, 2021 - This member is added by an implicit conversion from ArrayBuffer[A] to ArrowAssoc[ArrayBuffer[A]] performed by method ArrowAssoc in scala.Predef. ... A copy of this array buffer with an element appended. A mnemonic for +: vs. :+ is: the COLon goes on the COLlection side. ... scala> val a = List(1) a: List[Int] = List(1) scala> val b = a :+ 2 b: List[Int] = List(1, 2) scala> println(a) List(1)
EDUCBA
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Scala ArrayBuffer | Learn the Working for ArrayBuffer in Scala
June 6, 2023 - Scala ArrayBuffer is an indexed Sequence mutable data structure that allows us to add or change elements at a specific index. In ArrayBuffer we need not worry about the size; the size of an array buffer can be changed.
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Scala Programming Language
scala-lang.org › docu › files › collections-api › collections_24.html
Scala 2.8 Collections API -- Array Buffers
An ArrayBuffer buffer holds an array and a size. Most operations on an array buffer have the same speed as for an array, because the operations simply access and modify the underlying array. Additionally, array buffers can have data efficiently added to the end.
GitHub
github.com › scala › docs.scala-lang › blob › main › _overviews › scala-book › arraybuffer-examples.md
docs.scala-lang/_overviews/scala-book/arraybuffer-examples.md at main · scala/docs.scala-lang
scala> import scala.collection.mutable.ArrayBuffer scala> val nums = ArrayBuffer(1, 2, 3) val nums: ArrayBuffer[Int] = ArrayBuffer(1, 2, 3) scala> nums += 4 val res0: ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4) scala> nums += 5 += 6 val res1: ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, 6) scala> nums ++= List(7, 8, 9) val res2: ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, 6, 7, 8, 9) scala> nums -= 9 val res3: ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, 6, 7, 8) scala> nums -= 7 -= 8 val res4: ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4, 5, 6) scala> nums --= Array(5, 6) val res5: ArrayBuffer[Int] = ArrayBuffer(1, 2, 3, 4)
Author: scala
Allaboutscala
allaboutscala.com › tutorials › chapter-7-beginner-tutorial-using-scala-mutable-collection › scala-tutorial-learn-use-mutable-arraybuffer
Scala Tutorial - Learn How To Use Scala's Mutable ArrayBuffer
February 3, 2020 - In this Scala beginner tutorial, you will learn how to use Scala's Mutable ArrayBuffer: initialize, access element at specific index, add, remove elements.
Top answer 1 of 2
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Another way is to use to conversion method:
import scala.collection.mutable.ListBuffer
val arr: Array[Int] = Array(1, 2, 3, 4)
val buf: ListBuffer[Int] = arr.to[ListBuffer]
Type annotations on variables are, of course, superfluous, I've added them only for clarity.
to is very versatile, it allows conversion between arbitrary collections (that is, from anything Traversable to anything which has an appropriate CanBuildFrom instance in scope).
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5
How about:
val z = ListBuffer(y: _ *)
ListBuffer.apply accepts a varargs style sequence of elements. The signature is applyA: ListBuffer[A] In order to apply a sequence to a function like this, we use the syntax : _ *