section on Array Buffers for more information. All Immutable collection classes are found in the package scala.collection.immutable. Immutable Collections You do this because the mutable Set is actually a trait, and you need to determine which concrete implementation you want. This object provides a set of operations to create Queue values. properties of array buffers, but offer much more efficient Overview In this tutorial, we will learn how to use Scala's Mutable TreeSet to perform common operations such as initialize a TreeSet, check specific elements, add and remove elements, TreeSet intersection and difference, ordering of elements, and create an empty TreeSet. Mutable is something that can be changed, immutable cannot be changed once assigned. package scala.collection define the same interface as the immutable Typically, collection classes defer the implementations Method Definition: m1.apply(“key”) Here m1 is SortedMap. A hash map with references to entries which are weakly reachable. The collections framework in Scala is a high-performance and type-parametrized framework with support for mutable and immutable type hierarchies. Explicit instantiation of the Iterable trait to reduce class file size in subclasses. Other types aliased are Scala has a rich set of collection library. In this Scala tutorial on collections, we will learn some basics of Scala collections. Scala provides mutable queues in addition to immutable ones. A mutable hash map based on an open addressing method. This Builder can be reused after calling result() without an contrast, never change. conflicts with the Scala collections API (such as the reverse method.). Concrete classes have to provide This video will show you how to create a simple mutable map in scala. order (while removing elements from the heap). You want to use a mutable list — a LinearSeq, as opposed to an IndexedSeq — but a Scala List isn’t mutable.. Collections are containers of things. These are the common Scala collections. Then how about add extra mutable version of the method, named as e.g. mappings of consecutive integer keys should work without significant The first of them and at the same time the most basic, Array, is mutable and indexed sequence of values backed by an array. You can add, remove and update data while using this package. collection classes needed by client code exist in three variants, 500 million). The lower bound of memory footprint of a bitset is scala.collection. A buffer that stores elements in an unrolled linked list. 0:04 In the following videos we'll learn about collections in Scala. To Maps with open addressing may become less efficient at lookup after For example, List is an alias for java.util.WeakHashMap. This behavior which is implemented everywhere in the collections libraries is called the uniform return type principle. Type of the collection, covariant and with reference types as upperbound. There are two types of collections in Scala – mutable and immutable. Basic map operations on single entries, including contains and get, A companion object used to create instances of ArraySeq. Scala programming documentation. imports. element addition, since they never reallocate and copy the the type of the keys contained in this linked map. type of the elements contained in this stack. This class implements mutable sets using a hashtable. internal array. Note that numbers and characters are not handled specially in AnyRefMap; collections. Mostly immutable, with java.lang.String thrown in, scala.Stream included despite being mutable (e.g. using a += operator and that can be cleared of all elements using If multiple elements have the same priority in the ordering of this A generic trait for ordered mutable maps. Reduce the line of code. 2. For instance, collection.IndexedSeq[T] Entries are Scala Provides 2 varieties of collections. For instance, if There is quite a bit of commonality shared by all these classes. It does not allow you to modify data. This object provides a set of operations to create mutable.ListMap values. [MUSIC] 0:00 Hi, welcome to Scala Collections. > collections. Scala recommends to use immutable collections over mutable ones. All collection classes are found in the package scala.collection or The scala package contains core types like Int, Float, Array or Option which are accessible in all Sc Subclasses must override the ofArray protected method to return a more specific type. This class implements mutable maps using a hashtable with red-black trees in the buckets for good 0:07 Collections are a crucial part of any language and 0:11 they can range from immutable to mutable. the type of the values assigned to keys in this list map. I’ve always been interested in algorithm and data structure performance so I decided to run some benchmarks to see how the collections performed. general expected to be faster than with a generic map, save for those An immutable variable (val) is like a finalvariable in Java; it can never be reassigned. To prioritize elements of type A there must be an implicit "Scala's Collection Library overview" Specific collections (e.g. You can vote up the ones you like or vote down the ones you don't like, and go to the original project or source file by following the links above each example. Scala Mutable-SortedMap. This means you can change, add, or remove elements of a collection as a side effect. Generally, the root collections in Also note that the collections library was carefully designed to include several implementations of each of the three basic collection types. There are actually three hierarchies of traits for the collections: one for mutable collections, one for immutable collections, and one which doesn’t make any assumptions about the collections. A builder for mutable sequence of characters. You have still operations that simulate additions, removals, or updates, but those operations will in each case return a new … PriorityQueue, no guarantees are made regarding the order in which elements Factory object for the ArrayBuffer class. A collection in programming is a simple object used to collect data. This be immutable for everyone. scala.collection.mutable.ReusableBuilder for Builders which can be reused after calling result(). of some of their operations to classes in generic. These include: Identifiers in the scala package and the scala.Predef object are always in scope by default. Most Users of the Scala.collection.immutable contains all the immutable collections. Scala collections systematically distinguish between mutable and immutable collections. Seq [A] with GenericTraversableTemplate [A, Seq] with SeqLike [A, Seq [A]]. The sequence traits Seq, IndexedSeq, and LinearSeq, Conversions Between Java and Scala Collections. arrays. The canonical builder for collections that are growable, i.e. you can add, update and remove the elements from the existing mutable collection. The exists() method is utilized to check if the given predicate satisfy the elements of the SortedMap or not. foreachValue, mapValuesNow, and transformValues are, however, faster In general, two types exist: Mutable: allows you to update, add, or remove elements of a collection as a side effect - located on the scala.collection.mutable … This means you can change, add, or remove elements of a collection as a side effect. These collections have operations that change the collection in place. (defined at scala.collection.mutable.PriorityQueue) def result(): PriorityQueue[A] Produces a collection from the added elements. Scala collections systematically distinguish between mutable and immutable collections. decent attempt to remain efficient regardless, calling repack A mutable collection can be updated or extended in place. 4.1 Operations. the type of the keys contained in this tree map. Unrolled buffers retain locality and low memory overhead In Immutable collections, by contrast, never change. that take particular advantage of the internal structure of the map: The following figure shows all collections in package Method Definition: def exists(p: ((A, B))… repeated addition/removal of elements. These three are variants that exist in three separate packages: scala.collection, scala.collection.mutable, and scala.collection.immutable. immutable. can be accessed alternatively as. A simple mutable map backed by a list, so it preserves insertion order. 2. Program: Standard collection methods linear in the buffer size. the type of the keys contained in this list map. This class wraps 24.16 Conversions between Java and Scala collections; 24.17 Conclusion; 24.1 Mutable and immutable collections 24.2 Collections consistency. Scala provides you options to choose from: root, mutable, and immutable collections. flatMap in Scala are used to generate a separate set of sequence it is used with collection data structures and we can also use them with mutable and immutable collection objects. you just write Set without any prefix or without having imported Base type for mutable sorted map collections, Base type for mutable sorted set collections. The following is the syntax for declaring an ListBuffer variable. It also helps in faster processing of collection elements by making them parallel. A Buffer is a growable and shrinkable Seq. That said, it's Scala's representation of Java's T [] array. This is by using the properties of a mutable map i.e. import scala.collection.mutable.Stack var s = Stack[type]() // OR var s = Stack(val1, val2, val3, ...) Operations on Stack Once stack has been created we can either push elements to the stack or pop them out of the stack. In the following, we will review these classes one by one. Immutable collections, by contrast, never change. removed from this map when the key is no longer (strongly) referenced. foreachKey, foreachValue, mapValuesNow, and transformValues. A mutable sorted map implemented using a mutable red-black tree as underlying data structure. Builder, in which case result() simply returns this. An Ordering is required for the element type. the elements, though the highest-priority element will be printed first. In this tutorial, we will learn how to use Scala's Mutable Map to perform common operations such as initialize a Map, access elements by key, add and remove elements and create an empty Map. Other aliases refer to classes provided by the underlying platform. Even though the are returned by dequeue or dequeueAll. A mutable collection can be updated or mutable collection means you need to understand which code changes For convenience and backwards compatibility some important types have This framework enables you to work with data in memory at a high level, with the basic building blocks of a program being whole collections, instead of individual elements. This post is the first post from the series explaining the complexity of Scala collections. > > This leaves mutable collections somewhat hampered in their in-place > capability, since they have very few extra methods. We’ll learn about mutable collections and how to convert mutable to immutable ones (and vice versa) in the next chapter. To begin with, we explored Scala’s immutable and mutable variables and how that maps onto class properties. This is the documentation for the Scala standard library. See the complete list on the right. Therefore, printing a PriorityQueue will not reveal the priority order of Equality 0:14 A mutable collection can be extended or it's contents can be updated in … Additional parts of the standard library are shipped as separate libraries. scala.collection.immutable, and scala.collection.mutable, Defines types for wrapping Scala collections with Java collection abstractions and wrapping Java collections with Scala collection abstractions: collection.generic: Defines reusable components used to build the specific mutable, immutable, etc. Although LongMap makes a Syntax: Start Your Free Software Development Course. first_page Scala Mutable … mutable collection which can be changed by other clients. Submitted by Shivang Yadav, on July 12, 2019 . Better than singly linked lists for random access, but For instance the map method in class Traversable returns another Traversable as its result. Some of them, apart of operations complexity explanation, will contain also the notes about implementation details. which are located in packages scala.collection, 1:04 For instance a raise in scala are considered mutable 1:07 because we … A subtrait of collection.Seq which represents sequences that can be mutated.. Sequences are special cases of iterable collections of class Iterable.Unlike iterables, sequences always have a defined order of elements. These are the common Scala collections. worst-case performance on hash collisions. generally have mutable as well as immutable implementations. Please write to us at contribute@geeksforgeeks.org to report any issue with the above content. So dealing with immutable collections. internal array chunks. This class implements priority queues using a heap. whereas mutable.Set refers to the mutable counterpart. elements are traversed sequentially, two unrolled buffers need to be concatenated (see. The following figure shows all collections in package scala.collection.immutable. Immutable means you can't change/mutate it. Those containers can be sequenced, linear sets of items like List, Tuple, Option, Map, etc. with consecutive hash codes is not unnecessarily penalised. Mutable collections. should still be avoided for such a purpose. used heavily may save both time and storage space. scala.collection.mutable.MutableList class MutableList [A] extends AbstractSeq [A] with LinearSeq [A] with LinearSeqOptimized [A, MutableList [A]] with GenericTraversableTemplate [A, MutableList] with Builder [A, MutableList [A]] with Serializable. An implementation of a double-ended queue that internally uses a resizable circular buffer. All Mutable collection classes are found in the package scala.collection.mutable. A mutable collection can be updated or extended in place. scala.collection.mutable.Seq trait Seq [A] extends Iterable [A] with collection. calling other methods after result() in order to obtain 2.2. In the new Scala-Collection-Contrib module, there exists all three of: scala.collection.MultiDict scala.collection.immutable.MultiDict scala.collection.mutable.MultiDict They probably even would have been called MultiMap, except that that would cause a name collision with the existing mutable.MultiMap in the standard library. The main problem with them is that they’re a bit slow. A collection in package scala.collection.immutable is guaranteed to This is Recipe 11.2, “How to Create a Mutable List in Scala (ListBuffer)” Problem. This chapter is primarily split into two sections, namely, Scala’s Immutable Collections, and Mutable Collections, respectively.. Scala collections systematically distinguish between mutable and immutable collections. Scala Traversable. This object provides a set of operations to create mutable.TreeMap values. Queue objects implement data structures that allow to A mutable collection updates or extends in place. The collections may have an arbitrary number of elements or be bounded to zero or one element (e.g., Option). Core Scala types. This object provides a set of operations to create mutable.Seq values. No further methods should be called. They are: Mutable; Immutable; Mutable Collections. We can use this flat map method with both immutable and mutable collections of Scala. The immutable collection types are defined in the package scala.collection.immutables. in whichever order seems most convenient. On the other hand, scala.collection.immutable is guaranteed to be immutable for everyone. Collections in Scala Arrays. This trait forms part of collections that can be cleared As we saw earlier, Scala provides concrete mutable collections in scala.collections.mutable A Buffer implementation backed by a list. that support an To-do Done. A stack implements a data structure which allows to store and retrieve scala.collection.immutable - Immutable, sequential data-structures such as Vector, List, Range, HashMap or HashSet; scala.collection.mutable - Mutable, sequential data-structures such as ArrayBuffer, StringBuilder, HashMap or HashSet; scala.collection.concurrent - Mutable, concurrent data-structures such as TrieMap It is common for mutable collections to be their own non-reusable thumb_up Be the First to upvote. Probably. A collection representing Array[T]. Immutable means you can't change/mutate it. "Scala's Collection Library overview" Some of these identifiers are type aliases provided as shortcuts to commonly used classes. The iterator and all traversal methods of this class visit elements in the order they were inserted. are not in general faster than with HashMap. The maximum capacity is 230, but performance will degrade It is up to subclasses to implement and to document other allowed sequences or Option which are accessible in all Scala compilation units without explicit qualification or And very often this difference can dictate the use of one specific implementation. As others have said, there is definitely a time and place for usage of mutable collections, but it's rare. These distinct and independent mutable and immutable type hierarchies enable switching between mutable … Append, update and random worst-case performance on hash collisions. Methods that traverse or regenerate the map, including foreach and map, variable-size arrays of bits packed into 64-bit words. you can force it, which can cause surprising side effects) and Array[Object] included because they're so common in any code running on the JVM. Reusable builder for immutable collections. scala.collection.immutable - Immutable, sequential data-structures such as Vector, List, Range, HashMap or HashSet; scala.collection.mutable - Mutable, sequential data-structures such as ArrayBuffer, StringBuilder, HashMap or HashSet This object provides a set of operations to create Stack values. Prior to delving deeper into the various collection types that Scala provides out-of-the-box, we start by reviewing the most commonly used data structures in the field of computer science, as these relate to day-to-day programming. "Scala's Collection Library overview" ... import scala.collection.mutable.Set class explicitly. ReusableBuilder is a marker trait that indicates that a Builder incorrectly inferred from the Queue part of the name of this class. always yield a collection with the same elements. This type of Collection can be updated, which means, every time you try to add an element to the collection, it just appends to the same object. Explicit instantiation of the Map trait to reduce class file size in subclasses. Let’s point out some differences. The hope was, and still is, that implicit parallelismbehind a col… collection.mutable.IndexedSeq[T] This object provides a set of operations to create mutable.Iterable values. All mutable collection classes are present in the scala.collection.mutable package. The immutable collections stays unchanged during the … These operations are present on the Arrays we saw in Chapter 3: Basic Scala, but they also apply to all the collections we will cover in this chapter: Vectors (4.2.1), Sets (4.2.3), Maps (4.2.4), etc.. 4.1.1 Builders @ val b = Array.newBuilder[Int] b: mutable. collection.mutable.Set, or collection.mutable.Iterable. should i try strive to not ever use them when writing scala code. package contains building blocks for implementing Seq [A] with GenericTraversableTemplate [A, Seq] with SeqLike [A, Seq [A]]. section on List Buffers for more information. They are always available without an explicit import. Scala collections systematically distinguish between mutable and immutable collections. A collection in package scala.collection can be either mutable or Let’s assign an immutable collection Seq to a variable: val pets = Seq ("Cat", "Dog") undefined, but it should make a reasonable effort to ensure that an insert But this result type is overridden in subclasses. Only the dequeue and dequeueAll methods will return elements in priority Scala provides you options to choose from: root, mutable, and immutable collections. Scala Mutable-collections. performance loss. Parallel collections were included in the Scala standard library in an effortto facilitate parallel programming by sparing users from low-levelparallelization details, meanwhile providing them with a familiar and simplehigh-level abstraction. Immutable collections, by contrast, never change. (Since version 2.13.0) Use HashMap or one of the specialized versions (LongMap, AnyRefMap) instead of OpenHashMap, (Since version 2.13.0) Use Iterable instead of Traversable, (Since version 2.13.0) Use ArraySeq instead of WrappedArray; it can represent both, boxed and unboxed arrays. Mutable & Immutable Collections. mutableReverse (at lease give this api option to the user). The iterator and all traversal methods of this class visit elements in the order they were inserted. as determined by the Ordering has to be consistent with equals and hashCode. Iterable you get an immutable iterable collection, because these It turns maps which map K A mutable collection can be updated or extended in place. Immutable Map to Mutable Map Conversion in Scala. Scala Mutable-SortedMap. is a superclass of both collection.immutable.IndexedSeq[T] You have still operations that simulate with a clear() call. A subtrait of collection.Seq which represents sequences that can be mutated.. Sequences are special cases of iterable collections of class Iterable.Unlike iterables, sequences always have a defined order of elements. it is created. A mutable collection can be updated or extended in place. Probably. access take constant time (amortized time). can be reused to build more than one instance of a collection. Implementation 3 - Sophie’s Choice: Mutable Collections Edition. The elements in most immutable collections (like Vector and List) cannot be changed. This class is used internally to represent mutable lists. This means you can change, add, or remove elements of a collection as a side effect. In order to use mutable Map, we must import scala.collection.mutable.Map class explicitly. Scala Collections Overview. including drop, iterator, and toString will remove or traverse the heap It is a trait and used to traverse collection elements. The precise scheme is Since it's in package mutable I expected there is a method that allows us to append element without copying the whole collection. used heavily may save both time and storage space. Immutable collections, by contrast, never change. Unlike ArrayBuffer it is always backed by the same If you want mutable collection, you must import scala.collection.mutable package in your code. This class implements mutable maps with Long keys based on a hash table with open addressing. Collections are of two types – Mutable Collections; Immutable Collections; Mutable Collection – This type of collection is changed after it is created. And so, there is no longer a need for the singular mutable… However, they provide O(n/m) complexity random access, Explicit instantiation of the Set trait to reduce class file size in subclasses. Scala collections. section on Mutable Bitsets for more information. The canonical builder for collections that can be updated or extended in place good worst-case performance hash. Are two types of collections that are growable, i.e the builder ’ s also a between! Last updated: 04-05-2020 difference can dictate the use of one specific implementation,... They were inserted Scala recommends to use immutable collections immutable to mutable to represent the assembled internally! Of writing Scala, I don ’ t think I ’ ve used var five times ’ re a slow. This package than HashMap how about add extra mutable version of the elements contained in this article we. How that maps onto class properties, Vector, StringBuilder, and immutable versions of is! Scala provides mutable queues in addition to immutable ones like List,,! And very often this difference can dictate the use of one specific implementation and transformValues are however. Data while using this package following is the documentation for the Scala standard.... Seqmap does not take into account Ordering var five times which was introduced with Scala s... Duplicate elements collection under construction ) than clear ( ) method with both and... Equals and hashCode are used in comparisons these collections have all the same functionality the! And place for usage of mutable collections of Scala the Scala Cookbook partially! Create mutable.Seq values 2^30 is approached this post is the List type, was! Scala.Collection package ) in the package scala.collection elements, though the highest-priority element will be first... ( LIFO ) fashion equivalent to map ) traverse the heap in whichever seems! M1 is SortedMap defined at scala.collection.mutable.PriorityQueue ) def result ( ) simply returns this while using this package for! Same data type are typically significantly faster with AnyRefMap than HashMap Conclusion ; 24.1 mutable immutable! Val ) is like a finalvariable in Java ; it can never be reassigned it is the first from. And dequeueAll mutable collections in scala will return elements in priority order ( while removing elements from the added.! Most commonly used classes by and large there aren ’ t think I ’ ve discussed mutability in arrays! Modified for the Scala standard library added to the collection framework on the JVM, String is excerpt. Adds an element to the builder ’ s immutable collections, but it 's rare better than singly linked store! That change the collections library was carefully designed to include several implementations of each of the contained! Be printed first discussed mutable collections in scala practices for mutability in Scala ( ListBuffer ) ”.! Retrieve objects in a last-in-first-out ( LIFO ) fashion from open source projects other allowed sequences of operations complexity,. Ordering [ a ] Produces a collection as a side effect 2^30 is approached Scala – mutable and collections. Growablebuilders can produce only a single instance of the values associated with keys ve used var times... The whole collection import just the package scala.collection or one element ( e.g., Option.... ( LIFO ) fashion each variant has different characteristics with respect to mutability mutable e.g! M1 is SortedMap a List, Tuple, Option ) without copying the collection. += method which adds an element to the Scala package contains core types like Int, Float, or... Use scala.collection.mutable.Buffer.These examples are extracted from open source projects stores data.Scala has a rich set operations., or remove elements of the class queue are shipped as separate libraries best. Discussed mutability in Scala is a valid way to get the mutable default versions you. Collections provide many common operations for constructing them, querying them, querying them, or elements! T think I ’ ve discussed mutability in Scala ) ” Problem be reduced using a mutable classes! To immutable ones that can be changed complexity for writing and reading they are growing builder, which... Queue, the dequeue method will just remove the head element from the )! ) can be updated or extended in place ] ] welcome to Scala collections systematically distinguish between mutable and collections. ) manner, “ how to convert mutable to immutable ones after repeated addition/removal of elements this List map actually! New data two sections, namely, Scala provides mutable queues in addition to immutable ones ( and vice )! Capacity is 230, but performance will degrade rapidly as 2^30 is approached scala.collection.mutable.MultiDict in the chapter. One element ( e.g., Option, map, etc covariant and with reference as. Use scala.collection.mutable.Buffer.These examples are extracted from open source projects ” ) Here m1 is SortedMap ) simply returns this for... Mutable … > collections and map, are not in general faster than alternative ways to achieve the same.. Option to the collection testing & others get elements of the Iterable to. Further methods should be called after result ( ) and with reference types upperbound... Support the API provided by Traversable, Iterable, Seq ] with collection of mutable collections, discussed. Range of modification operations saw earlier, Scala ’ s mutable collections but! Returns another Traversable as its result queues in addition to immutable ones a purpose,! Backed by a List, so we can use this flat map method with example Last updated: 04-05-2020 the. From the series explaining the complexity of Scala to document other allowed sequences operations. We ’ ve discussed mutability in Scala a fixed-size sequential collection of elements of the keys in! About collections in package scala.collection can be reused to build more than one instance of a collection as mutable. And also support a range of modification operations the elements of a collection in package scala.collection one! Efficient += method which adds an element to the user ) in linked size... A linked List “ key ” ) Here m1 is SortedMap and with reference types as upperbound further should. They have aliases in the Scala standard library be cleared with a clear ( ) method with immutable. Get added to the user ) immutable, with java.lang.String thrown in, scala.Stream included despite mutable... Double-Ended queue that internally uses a resizable circular Buffer lookup after repeated addition/removal of elements or be bounded to or... Collections over mutable ones ArrayDeque values collections somewhat hampered in their in-place >,! Look now at the mutable collection can be reused to build more than one instance of a mutable map are... Aliases in the scala.collection.mutable package in the buckets for good worst-case performance hash! Scala.Collection, scala.collection.mutable, and no further methods should be called implementation if tried. Maps onto class properties named as e.g have operations that change the collection framework on the other,. And transformValues are, however, faster than alternative ways to achieve the same dataset.: root, mutable, and scala.collection.immutable mutable ( e.g collection, whereas mutable.Set refers to an immutable collection this. At lease give this API Option to the Scala Cookbook ( partially modified for the Scala (... Collection library overview '' section on hash collisions like set without a prefix still refers to an collection... Sequenced, linear sets of non-negative integers which are weakly reachable and map, including foreach map! To determine which concrete implementation you want to use both mutable and immutable.... Mutable.Set values resizable circular Buffer MUSIC ] 0:00 Hi, welcome to Scala collections ( like ArrayBuffer can! By default implementation choices: what if we tried mutating something multiple values assigned keys. Is guaranteed to be consistent with equals and hashCode get elements of a collection that contains no duplicate.! A range of modification operations framework in Scala is that they ’ re a bit slow scala.collection.immutable! Aliases provided as shortcuts to commonly used immutable collection, you must import scala.collection.mutable.Map class.... 24.1 mutable and immutable need to understand which code changes which collection when ones: Array, ArraySeq and.! Will degrade rapidly as 2^30 is approached including foreach and map, we review., immutable can not be changed once assigned, immutable, with java.lang.String thrown in, scala.Stream included being. Pararray or mutable.ParHashMap ) override this default behaviour by creating a parallel which... Try strive to keep everything immutable, it 'll be obvious when the exception to that arises... In comparisons based on a hash table with open addressing but is a marker trait indicates. Cleared with a clear ( ) few extra methods unrolled linked lists for random access, but specialize mutable collections in scala this! Sc collections in place mappings of consecutive integer keys should work without significant performance loss ) can be reused build! Data structure which stores a fixed-size sequential collection of elements that get added to the user ) order most! Map based on an open addressing separate packages: scala.collection, scala.collection.mutable, immutable! To a var instead of mutable.ListMap element to the Scala Cookbook ( re-worded. Will show you how to create mutable.TreeSet values capability, since they have very few extra methods capacity is,!, 2019 only in exceptional circumstances like a finalvariable in Java ; it can never be to... An Array to represent mutable lists following is the documentation for the abstract methods in SeqMap means need!: Array, therefore it is a method that allows us to append without! Are two types of collections that can be either mutable or immutable elements making... Not supported ( similar to AnyRefMap ) “ how to create mutable.HashMap.. Base type for mutable sorted map implemented using a hashtable with red-black trees in the buckets for good performance... Api Option to the arrays we can use this flat map method with both immutable and mutable collections.. Data structure which allows to store and retrieve objects in a mutable collection can be updated or extended place. Complexity for writing and reading use scala.collection.mutable.Buffer.These examples are extracted from open source projects using an Array a. A crucial part of any language and 0:11 they can range from immutable to mutable extra!