How to use getOrElseUpdate in scala.collection.mutable.HashMap? - scala

Question

The example code counts each word's occurrences in given input file:
object Main {
def main(args: Array[String]) {
val counts = new scala.collection.mutable.HashMap[String, Int]
val in = new Scanner(new File("input.txt"))
while (in.hasNext()) {
val s: String = in.next()
counts(s) = counts.getOrElse(s, 0) + 1 // Here!
}
print(counts)
}
}
Can the highlighted with comment line be rewritten using the getOrElseUpdate method?
P.S. I am only at the 4th part of the "Scala for the impatient", so please don't teach me now about functional Scala which, I am sure, can be more beautiful here.
Thanks.

Answer 1

If you look at the doc you'll see the next:
If given key is already in this map, returns associated value.
Otherwise, computes value from given expression op, stores with key in
map and returns that value.
, but you need to modify map anyway, so getOrElseUpdate is useless here.
You can define default value, which will return if key doesn't exist. And use it the next way:
import scala.collection.mutable.HashMap
object Main {
def main(args: Array[String]) {
val counts = HashMap[String, Int]().withDefaultValue(0)
val in = new Scanner(new File("input.txt"))
while (in.hasNext()) {
val s: String = in.next()
counts(s) += 1
}
print(counts)
}
}