Activator UI ,java.lang.NoClassDefFoundError: - scala

Question

I'm trying to create basic scala project in intellij by using the Activator UI
I'm importing the project to the ide and it compile well
But when im trying to run simple code im getting
Exception in thread "main" java.lang.NoClassDefFoundError: scala/collection/GenTraversableOnce$class
at akka.util.Collections$EmptyImmutableSeq$.<init>(Collections.scala:15)
at akka.util.Collections$EmptyImmutableSeq$.<clinit>(Collections.scala)
at akka.japi.Util$.immutableSeq(JavaAPI.scala:209)
at akka.actor.ActorSystem$Settings.<init>(ActorSystem.scala:150)
at akka.actor.ActorSystemImpl.<init>(ActorSystem.scala:470)
at akka.actor.ActorSystem$.apply(ActorSystem.scala:111)
at akka.actor.ActorSystem$.apply(ActorSystem.scala:104)
at reactivemongo.api.MongoDriver$.reactivemongo$api$MongoDriver$$defaultSystem(api.scala:378)
at reactivemongo.api.MongoDriver$$anonfun$3.apply(api.scala:305)
at reactivemongo.api.MongoDriver$$anonfun$3.apply(api.scala:305)
at scala.Option.getOrElse(Option.scala:120)
at reactivemongo.api.MongoDriver.<init>(api.scala:305)
at example.App$.main(App.scala:10)
at example.App.main(App.scala)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)
When the project is loaded there is an error in the project structure
sbt:scala 2.11.2 not in use
What went wrong with the activator ui intellij project generation ?
thanks
miki

Answer 1

I came across this when trying to run spark. This is a incompatibility error between the scala version which was used to compile the dependancy and the version of scala which is used to run your project.
Removing my scala version specification was a hacky way to solve the problem:
// build.sbt
name := "SparkTest"
version := "1.0"
scalaVersion := "2.11.4" <-- remove this
libraryDependencies += "org.apache.spark" % "spark-core_2.10" % "1.3.0"