在用sbt跑scala spark mllib的(SparkPi.scala)例子时，遇到了HashSet方法不存在的错误；这个错误发生在运行阶段，具体错误信息如下：

[error] (run-main-0) java.lang.NoSuchMethodError: scala.collection.immutable.HashSet$.empty()Lscala/collection/immutable/HashSet;
java.lang.NoSuchMethodError: scala.collection.immutable.HashSet$.empty()Lscala/collection/immutable/HashSet;
    at akka.actor.ActorCell$.<init>(ActorCell.scala:305)
    at akka.actor.ActorCell$.<clinit>(ActorCell.scala)
    at akka.actor.RootActorPath.$div(ActorPath.scala:152)
    at akka.actor.LocalActorRefProvider.<init>(ActorRefProvider.scala:465)
    at akka.remote.RemoteActorRefProvider.<init>(RemoteActorRefProvider.scala:124)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:422)
    at akka.actor.ReflectiveDynamicAccess$$anonfun$createInstanceFor$2.apply(DynamicAccess.scala:78)
    at scala.util.Try$.apply(Try.scala:191)

通过搜索之后发现好多人遇到了同样的问题， 问题是由于scala版本兼容性导致（我的运行环境是 spark1.3/scala 2.11）; 最后用 scala 2.10版替换掉2.11版，问题得到了解决。