HashMap in Scala

HashMap is a part of Scala Collection’s. It is used to store element and return a map. A HashMap is a combination of key and value pairs which are stored using a Hash Table data structure. It provides the basic implementation of Map.

Syntax:

var hashMapName = HashMap("key1"->"value1", "key2"->"value2", "key3"->"value3", ...) 

We must import scala.collection.mutable.HashMap for HashMap.

Operation performed by HashMap

Creating an HashMap:

Below is the example to create HashMap. In below code, we can see an empty HashMap is created then a HashMap is created with values.

// Scala program to create or print HashMap
import scala.collection.mutable.HashMap

// Creating object
object Geeks
{

    // Main method
    def main(args: Array[String])
    {
        // Creating empty HashMap
        var hashMap = new HashMap()

        // Creating HashMap with values
        var hashMap2 = HashMap("C"->"Csharp", "S"->"Scala", "J"->"Java")

        // Printing HashMap
        println(hashMap)
        println(hashMap2)
    }
}

Output:

Map()
Map(S -> Scala, J -> Java, C -> Csharp)

Adding and Accessing Elements :

In the below example, A HashMap is created. add elements and access elements also performed.

// Scala program to Adding and Accessing Elements HashMap
import scala.collection.mutable.HashMap

// Creating object
object Geeks
{

    // Main method
    def main(args: Array[String])
    {
        // Creating HashMap
        var hashMap = HashMap("C"->"Csharp", "S"->"Scala", "J"->"Java")

        // Iterating elements
        hashMap.foreach
        {
            case (key, value) => println (key + " -> " + value)
        }

        // Accessing value by using key
        println(hashMap("S"))

        // Adding element
        var HashMap2 = hashMap + ("P"->"Perl")
        HashMap2.foreach
        {
            case (key, value) => println (key + " -> " + value)
        }
    }
}

Output:

S -> Scala
J -> Java
C -> Csharp
Scala
S -> Scala
P -> Perl
J -> Java
C -> Csharp

Removing an element from HashMap :
A HashMap is created than removing an element is performed using – sign. Below is the example to removing an element from HashMap.

// Scala program to removing Element HashMap
import scala.collection.mutable.HashMap

// Creating object
object Geeks
{

    // Main method
    def main(args: Array[String])
    {
        // Creating HashMap
        var hashMap = HashMap("C"->"Csharp", "S"->"Scala", "J"->"Java")

        // Iterating elements
        hashMap.foreach
        {
            case (key, value) => println (key + " -> " + value)
        }

        // Removing an element
        hashMap -= "C"

        println("After Removing")
        hashMap.foreach
        {
            case (key, value) => println (key + " -> " + value)
        }
    }
}

Output:

S -> Scala
J -> Java
C -> Csharp
After Removing
S -> Scala
J -> Java