How to run Scala script using spark-submit (similarly to Python script)?

I try to execute a simple Scala script using Spark as described in the Spark Quick Start Tutorial. I have not troubles to execute the following Python code:

"""SimpleApp.py"""
from pyspark import SparkContext

logFile = "tmp.txt"  # Should be some file on your system
sc = SparkContext("local", "Simple App")
logData = sc.textFile(logFile).cache()

numAs = logData.filter(lambda s: 'a' in s).count()
numBs = logData.filter(lambda s: 'b' in s).count()

print "Lines with a: %i, lines with b: %i" % (numAs, numBs)

I execute this code using the following command:

/home/aaa/spark/spark-2.1.0-bin-hadoop2.7/bin/spark-submit hello_world.py

However, if I try to do the same using Scala, I have technical problems. In more detail, the code that I try to execute is:

* SimpleApp.scala */
import org.apache.spark.SparkContext
import org.apache.spark.SparkContext._
import org.apache.spark.SparkConf

object SimpleApp {
  def main(args: Array[String]) {
    val logFile = "tmp.txt" // Should be some file on your system
    val conf = new SparkConf().setAppName("Simple Application")
    val sc = new SparkContext(conf)
    val logData = sc.textFile(logFile, 2).cache()
    val numAs = logData.filter(line => line.contains("a")).count()
    val numBs = logData.filter(line => line.contains("b")).count()
    println("Lines with a: %s, Lines with b: %s".format(numAs, numBs))
  }
}

I try to execute it in the following way:

/home/aaa/spark/spark-2.1.0-bin-hadoop2.7/bin/spark-submit hello_world.scala

As the result I get the following error message:

Error: Cannot load main class from JAR file

Does anybody know what I am doing wrong?