Exception throws when running spark pi in Intellij Idea that scala.collection.Seq is not found

[Todd]

I cloned the code from https://github.com/apache/spark to my machine. It can 
compile successfully,
But when I run the sparkpi, it throws an exception below complaining the 
scala.collection.Seq is not found.
I have installed scala2.10.4 in my machine, and use the default profiles: 
window,scala2.10,maven-3,test-java-home.
In Idea, I can find that the Seq class is on my classpath:





Exception in thread "main" java.lang.NoClassDefFoundError: scala/collection/Seq
    at org.apache.spark.examples.SparkPi.main(SparkPi.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:140)
Caused by: java.lang.ClassNotFoundException: scala.collection.Seq
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
    ... 6 more