ListMap in Scala

Last Updated : 09 Aug, 2019

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 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 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 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 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()

My Personal Notes

Related Articles

Operaion performed by ListMap