How to merge lists in Scala

Last Updated : 13 Jul, 2021

A list is a collection which contains immutable data. List represents linked list in Scala. The Scala List class holds a sequenced, linear list of items. Lists are immutable and represents a linked list.
Syntax of List:

val variable_name: List[type] = List(item1, item2, item3)
or
val variable_name = List(item1, item2, item3)

Below are three different way to merge lists:

using the ++
Using :::
Using concat

Following are the various ways to merge two lists in Scala:

By using ++ method

Example:

Scala

// Scala program to merge lists
 
// Creating object 
object GFG 
{ 
    // Main method 
    def main(args:Array[String]) 
    { 
        // Creating Lists 
        val a = List("geeks", "for", "geeks") 
        val b = List("is", "a", "computer science", "portal")
        val c = List("for", "geeks")
         
        // Merging Lists
        val d = a ++ b ++ c
        println("After merging lists ") 
        println(d) 
    } 
}     
    

Output:

After merging lists 
List(geeks, for, geeks, is, a, computer science, portal, for, geeks)

In above example we are using ++ method to concatenate lists. This method is used consistently across immutable collections

By using :::

If we using the List class frequently, we may prefer using ::: method.
Example:

Scala

// Scala program to merging two lists
 
// Creating object 
object GFG 
{ 
    // Main method 
    def main(args:Array[String]) 
    { 
        // Creating a List. 
        val a = List("Languages", "are") 
        val b = List("C++", "Java", "C#", "Python", "Scala")
         
        // Merging two lists
        val c = a ::: b
         
        println("After merging lists") 
        println(c) 
    } 
}     
    

By using concat method

Example:

Scala

// Scala program merging two lists
 
// Creating object 
object GFG 
{ 
    // Main method 
    def main(args:Array[String]) 
    { 
        // Creating a List. 
        val a = List(1, 2, 3) 
        val b = List(4, 5, 6)
         
        // concatenate two lists
        val c = List.concat(a, b)
        println("After merging lists") 
        println(c) 
    } 
}     

Output:

After merging lists
List(1, 2, 3, 4, 5, 6)

How to Sort a list in Scala?

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How to merge lists in Scala

By using ++ method

Scala

By using :::

Scala

By using concat method

Scala

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