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How to sort a Scala Map by key
  • Last Updated : 13 Aug, 2019

Map is same as dictionary which holds key:value pairs. In this article, we will learn how to sort a Scala Map by key. We can sort the map by key, from low to high or high to low, using sortBy.
Syntax :

mapName.toSeq.sortBy(_._1):_*

Let’s try to understand it with better example.
Example #1:




// Scala program to sort given map by key
import scala.collection.immutable.ListMap
  
// Creating object 
object GfG 
  
    // Main method 
    def main(args:Array[String]) 
    
      
        // Creating a map 
        val mapIm = Map("Zash" -> 30
                        "Jhavesh" -> 20
                        "Charlie" -> 50
                          
        // Sort map by key
        val res = ListMap(mapIm.toSeq.sortBy(_._1):_*)
        println(res)
    
Output:
Map(Charlie -> 50, Jhavesh -> 20, Zash -> 30)

Example #2:




// Scala program to sort given map by key
import scala.collection.immutable.ListMap
  
// Creating object 
object GfG 
  
    // Main method 
    def main(args:Array[String]) 
    
      
        // Creating a map 
        val mapIm = Map("Zash" -> 30
                        "Jhavesh" -> 20
                        "Charlie" -> 50
          
        // reverse map in ascending order
        val res = ListMap(mapIm.toSeq.sortWith(_._1 < _._1):_*)
        println(res)
    
Output:
Map(Charlie -> 50, Jhavesh -> 20, Zash -> 30)

Example #3:




// Scala program to sort given map by key
import scala.collection.immutable.ListMap
  
// Creating object 
object GfG 
  
    // Main method 
    def main(args:Array[String]) 
    
      
        // Creating a map 
        val mapIm = Map("Zash" -> 30
                        "Jhavesh" -> 20
                        "Charlie" -> 50
          
        // reverse map in descending order
        val res = ListMap(mapIm.toSeq.sortWith(_._1 > _._1):_*)
        println(res)
    
Output:
Map(Zash -> 30, Jhavesh -> 20, Charlie -> 50)



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