ListMap in Scala - GeeksforGeeks

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

Operaion performed by ListMap

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