CODEWITHSUNDEEP
scala
Wei-Fan Chiang
Wei-Fan Chiang

Reputation: 13

Sort a typed Scala HashMap

I searched the answers of sorting a scala HashMap. Which is 

opthash.toSeq.sortBy(_._1)

I just want to sorted by key, thus the above solution should apply.

However, here is my situation that the above solution resulted in an error: 

def foo (opthash : HashMap[Int,String]) = {
    val int_strin_list = opthash.toSeq.sortBy(_._1);
    "return something"
}

I got the following error message: 

value sortBy is not a member of Seq[(Int, String)]

Did I miss something? I am pretty sure that sortBy is a member of type Seq...

Any suggestion will be appreciated.

Upvotes: 1

Views: 1494

Answers (1)

Vinicius Miana
Vinicius Miana

Reputation: 2067

Make sure to use Scala HashMap and not java HashMap. Are you sure you did not misread the error message?

scala> import java.util.HashMap
import java.util.HashMap

scala> def foo (opthash : HashMap[Int,String]) = {
     |     val int_strin_list = opthash.toSeq.sortBy(_._1);
     |     "return something"
     | }
<console>:13: error: value toSeq is not a member of java.util.HashMap[Int,String]
           val int_strin_list = opthash.toSeq.sortBy(_._1);
                                        ^

The right way to go is:

scala> import scala.collection.immutable.HashMap
import scala.collection.immutable.HashMap

scala> def foo (opthash : HashMap[Int,String]) = {
     |     val int_strin_list = opthash.toSeq.sortBy(_._1);
     |     "return something"
     | }
foo: (opthash: scala.collection.immutable.HashMap[Int,String])String

Or too use the mutable HashMap if that is the case.

Upvotes: 2

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