What is the syntax for adding an element to a scala collection mutable Map

Question

What is the syntax for adding an element to a scala collection mutable Map    Here are some failed attempts   val map   scala collection mutable Map  map  mykey      myval   map     mykey  - gt   myval   map put  mykey   myval

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When you say  val map   scala collection mutable Map   you are not creating a map instance  but instead aliasing the Map type   map  collection mutable Map type   scala collection mutable Map  fae93e   Try instead the following   scala gt  val map   scala collection mutable Map String  Int    map  scala collection mutable Map String Int    Map    scala gt  map  asdf     9  scala gt  map res6  scala collection mutable Map String Int    Map  asdf 9

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Create a new immutable map   scala gt  val m1   Map  k0  - gt   v0      m1  scala collection immutable Map String String    Map k0 - gt  v0    Add a new key value pair to the above map  and create a new map  since they re both immutable    scala gt  val m2   m1     k1  - gt   v1                m2  scala collection immutable Map String String    Map k0 - gt  v0  k1 - gt  v1

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The point is that the first line of your codes is not what you expected   You should use   val map   scala collection mutable Map A B      You then have multiple equivalent alternatives to add items   scala gt  val map   scala collection mutable Map String String    map  scala collection mutable Map String String    Map     scala gt  map  k1      v1   scala gt  map res1  scala collection mutable Map String String    Map  k1 v1     scala gt  map     k2  - gt   v2  res2  map type   Map  k1 v1    k2 v2     scala gt  map put  k3    v3   res3  Option String    None  scala gt  map res4  scala collection mutable Map String String    Map  k3 v3    k1 v1    k2 v2     And starting Scala 2 13   scala gt  map addOne  k4  - gt   v4   res5  map type   HashMap k1 - gt  v1  k2 - gt  v2  k3 - gt  v3  k4 - gt  v4

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Create a mutable map without initial value   scala gt  var d  collection mutable Map Any  Any    d  scala collection mutable Map Any Any    Map     Create a mutable map with initial values   scala gt  var d  collection mutable Map Any  Any   a - gt 3 1- gt 234 2- gt  test   d  scala collection mutable Map Any Any    Map 2 - gt  test  a - gt  3  1 - gt  234    Update existing key-value   scala gt  d  a     ABC    Add new key-value   scala gt  d 100    new element    Check the updated map   scala gt  d res123  scala collection mutable Map Any Any    Map 2 - gt  test  100 - gt  new element  a - gt  ABC  1 - gt  234

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var map Map String  String    Map   var map1   map     quot red quot  - gt   quot  FF0000 quot   println map1

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var test   scala collection mutable Map empty String  String  test  myKey      myValue

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As always  you should question whether you truly need a mutable map   Immutable maps are trivial to build   val map   Map     mykey  - gt   myval      myotherkey  - gt   otherval      Mutable maps are no different when first being built   val map   collection mutable Map     mykey  - gt   myval      myotherkey  - gt   otherval     map     nextkey  - gt   nextval    In both of these cases  inference will be used to determine the correct type parameters for the Map instance   You can also hold an immutable map in a var  the variable will then be updated with a new immutable map instance every time you perform an  update   var map   Map     mykey  - gt   myval      myotherkey  - gt   otherval     map     nextkey  - gt   nextval    If you don t have any initial values  you can use Map empty   val map   Map String  String    Map empty   immutable val map   Map empty String String    immutable val map   collection mutable Map empty String String    mutable

[scala] What is the syntax for adding an element to a scala.collection.mutable.Map?

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