Single iteration => Multiple output collections from Java to Scala -

i'm trying convert java code scala code. challenge ensure converted scala code doesn't end doing inefficient when compared original java one. e.g. when trying convert following code:

class person {     string name;     integer age;     character gender; }  public class testjava {     public static void main(string[] args) {         final list<person> persons = new arraylist<>();         final list<person> males = new arraylist<>();         final list<person> anames = new arraylist<>();         final list<person> seniors = new arraylist<>();         (final person p: persons) {             if (p.gender == 'm') {                 males.add(p);             }             if (p.age >= 60) {                 seniors.add(p);                             }             if (p.name.startswith("a")) {                 anames.add(p);             }                     }     } } 

since java relies on mutation, code looks logical. but, want convert scala equivalent without looping on collection multiple times (3 times in case).

i can of course use mutable list scala library , achieve same thing done java wondering if possible generate multiple collections given sequence/collection in functional/scala way without iterating on collection n times n criteria count. in advance!

one purely functional , immutable way have generic function separates collections buckets, predicate:

case class person(name: string, age: int, gender: string)  def bucketsbypredicate(people: seq[person], predicates: seq[person => boolean]) = {   people.foldleft(predicates.map(predicate =>     (predicate, list.empty[person])   )) { case (predicates, person) =>       predicates.map { case (predicate, members) =>         (predicate, if(predicate(person)) person :: members else members)       }   }.map(_._2) } 

then example usage be:

val olderthan60 = (p: person) => p.age >= 60 val male = (p: person) => p.gender == "m" val seq(olderthan60people, malepeople) = bucketsbypredicate(people, seq(olderthan60, male))