Scala - finding sequence members that are of a certain type's child type -

i have following situation:

java lib class:

class libclass {   arraylist<libclass> children; } 

my program scala code:

abstract class myclass extends libclass {   def boom { }   def boommyclassinstances  // ??? }  class lala extends myclass class hoho extends myclass 

the question is: in method boommyclassinstances scala-ish way children of myclass, stored in children arraylist can call common boom method upon them all?

my try is:

def boommyclassinstances {   children.toarray.map { case mc: myclass => mc.boom } } 

is correct approach? pick children of myclass , right scala way that, or have type bounds?

check out gentraversablelike.collect. signature traversable[a].collect[b <: a](f: ~> b): traversable[b], is, takes collection elements of type a , partial function f a b, , returns collection of static element-type b, b subtype of a.

val myclassinstances: list[myclass] =   children.tolist.collect{case mc: myclass => mc} 

since map expects total function, try above fail scala.matcherror in case children not contain instances of myclass. can work around using option or flatmap, collect seems scala-ish way of achieving want.