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ListMap in Scala

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  • Last Updated : 04 Aug, 2021
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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.
 

Operation performed by ListMap

Creating an ListMap: 
In below code we can see a ListMap is created with values.

Scala




// Scala program to create or print ListMap
import 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




// Scala program to Adding and Accessing Elements ListMap
import 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




// Scala program to removing Element from ListMap
import 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




// Scala program to Create an empty ListMap
import 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()

 


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