Finding second highest frequency of characters in String

Write a method that accepts a String and returns the character with the second highest frequency. For example "aabbbc" would return 'a'. If the string contains spaces, they can be disregarded from the count. Note: my implementation returns a tuple (char, count) but that is just a matter of only returning the char itself.

	package puzzlers
	import scala.collection.mutable.{Map => MMap}
	object HighestFrequencyPuzzle {
	def stringToCharFrequencyMap(source: String): MMap[Char, Int] = {
	source.filter(c => c!=' ').foldLeft(MMap[Char, Int]())((map, char) => {
	map.update(char, map.getOrElseUpdate(char, 0) + 1)
	map
	})
	}
	def getNthHighestFrequency(source: String, n: Int): (Char, Int) =
	stringToCharFrequencyMap(source).toList.sortBy(_._2).reverse.drop(n -1).take(1)(0)
	def main(args: Array[String]): Unit = {
	val highest = getNthHighestFrequency("abecbb cdcbef", 1)
	println(highest)
	val secondHighest = getNthHighestFrequency("abecbb cdcbef", 2)
	println(secondHighest)
	}
	}
	/** output
	(b,4)
	(c,3)
	**/

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