java.lang.NoClassDefFoundError: scala/Product$class

def main(args: Array[String]): Unit = {
    val conf = new SparkConf().setMaster("local").setAppName("wc")
    val sc = new SparkContext(conf)

    val text = sc.textFile("test.txt")
    val words = text.flatMap{line => line.split(" ")}
    val pairs = words.map{word => (word, 1)}
    val results = pairs.reduceByKey(_+_)
    val sorted = results.sortByKey(false)
    sorted.foreach{x => println(x)}
  }

以上程序运行出现如下异常：

# java.lang.NoClassDefFoundError: scala/Product$class
``
原因是Spark是基于scala 2.11编译的，而环境使用了最新的2.12的scala的编译版本；

your sbt build file is not right. your scala version is 2.12.x but you are using libraries compiled in scala version 2.11. use the sbt settings shown below

note: I changed of the version of scalatest as 2.x versions are no longer supported for 2.12 version of scala

scalaVersion := "2.12.1"

libraryDependencies ++= Seq(
"org.scala-js" %% "scalajs-test-interface" % "0.6.14",
"org.scalatest" %% "scalatest" % "3.0.1", //version changed as these the only versions supported by 2.12
"com.novocode" % "junit-interface" % "0.11",
"org.scala-lang" % "scala-library" % scalaVersion.value
)
remember to do reload, clean and compile in your sbt console to start clean compile