Immutable maps Implemented by using a list-based data structure. The Scala List class holds a sequenced, linear list of items. We must import scala.collection.mutable.ListMap for ListMap. ListMap collection used only for a small number of elements.
Syntax:
var listMapName = ListMap("k1"->"v1", "k2"->"v2", "k3"->"v3", ...) Here, k is key and v is value.
Operaion performed by ListMap
Creating an ListMap:
In below code we can see a ListMap is created with values.
// Scala program to create or print ListMapimport scala.collection.immutable.ListMap // Creating object object Geeks { // Main method def main(args: Array[String]) { // Creating ListMap with values var listMap = ListMap("C"->"Csharp", "S"->"Scala", "J"->"Java") // Printing ListMap println(listMap) } } |
Output:
Map(C -> Csharp, S -> Scala, J -> Java)
Adding and accessing elements :
A ListMap is created, add elements and access elements also performed.
// Scala program to Adding and Accessing Elements ListMapimport scala.collection.mutable.ListMap // Creating object object Geeks { // Main method def main(args: Array[String]) { // Creating ListMap var listMap = ListMap("C"->"Csharp", "S"->"Scala", "J"->"Java") // Iterating elements listMap.foreach { case (key, value) => println (key + " -> " + value) } // Accessing value by using key println(listMap("S")) // Adding element var ListMap2 = listMap + ("P"->"Perl") ListMap2.foreach { case (key, value) => println (key + " -> " + value) } } } |
Output:
J -> Java C -> Csharp S -> Scala Scala P -> Perl C -> Csharp J -> Java S -> Scala
Removing an element from ListMap :
A ListMap is created than removing an element is performed using – sign. Below is the example to removing an element from ListMap.
// Scala program to removing Element from ListMapimport scala.collection.mutable.ListMap // Creating object object Geeks { // Main method def main(args: Array[String]) { // Creating ListMap var listMap = ListMap("C"->"Csharp", "S"->"Scala", "J"->"Java") // Iterating elements listMap.foreach { case (key, value) => println (key + " -> " + value) } // Removing an element listMap -= "C" println("After Removing") listMap.foreach { case (key, value) => println (key + " -> " + value) } } } |
Output:
J -> Java C -> Csharp S -> Scala After Removing J -> Java S -> Scala
Creating an empty ListMap:
An empty ListMap is created either by calling its constructor or using ListMap.empty method.
// Scala program to Create an empty ListMapimport scala.collection.mutable.ListMap // Creating object object Geeks { // Main method def main(args: Array[String]) { // Creating an empty list map by calling constructor var ListMap1 = new ListMap() // Creating an empty list map by using .empty method var ListMap2 = ListMap.empty // Printing empty ListMap println(emptyListMap1) println(emptyListMap2) } } |
Output:
Map() Map()
