How can I join an iterable of strings in Scala?

Question

How do I "join" an iterable of strings by another string in Scala?

val thestrings = Array("a","b","c") val joined = ??? println(joined)

I want this code to output a,b,c (join the elements by ",").

outis · Accepted Answer · 2025-03-20 23:39:54Z

511

How about mkString ?

theStrings.mkString(",")

A variant exists in which you can specify a prefix and suffix too.

See here for an implementation using foldLeft, which is much more verbose, but perhaps worth looking at for education's sake.

edited Mar 20 at 23:39

outis

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answered Nov 23, 2012 at 12:49

Brian Agnew

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4 Comments

Ferdy Over a year ago

Note that the foldLeft implementation assumes a non-empty list

Niko Gamulin Over a year ago

Thanks! In case anyone wants to enclose string elements in quotes, mkString is also helpful: theStrings.mkString("'", "','", "'")

Davos Over a year ago

@Frawr That page links to a bunch of examples oldfashionedsoftware.com/2009/07/30/… which includes an implementation that uses pattern matching for the empty list (Nil) case. Modifying it to mimic mkString would be like this:

def mkFoldLeftString[A](list:List[String], delim:String = ","): String = list match { case head :: tail => tail.foldLeft(head)(_ + delim + _) case Nil => "" }

Floegipoky Over a year ago

The langref.org link is dead

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