How to get Input in Scala

Below is a simple example which details on how to fetch input from the console.
Instructions on how to run it.
a.Copy the below mentioned code into a file named SourceInput .
b. Run > scalac SourceInput .scala
c. Run > scala SourceInput

import scala.io._
object SourceInput {
 
 def main(args: Array[String]) {
   println("Enter some numbers and press ctrl-D (Unix/Mac) ctrl-C (Windows)")
   val input = Source.fromInputStream(System.in)
   val lines = input.getLines.toSeq
   println("Sum "+lines.mkString)

  }
  def toInt(in: String): Option[Int] =
    try {
      Some(Integer.parseInt(in.trim))
    } catch {
      case e: NumberFormatException => None
    }
  def sum(in: Seq[String]) = {
    val ints = in.flatMap(s => toInt(s))
    ints.foldLeft(0)((a, b) => a + b)
  }
}

Observations:
a. Methods are defined as def.
b. Vals are scala's way of defining Immutable objects.
c. Source is a scala class for fetching Inputstream from System.in
d. s => toInt(s) is scala's way of handling lamda expression. See Post on why scala for more on lamda calculus.
e. Option[Int] is a elegant way of handling the way values are returned.Option is a container that one or zero things.If it holds zero elements ,its None which is a signleton,which means that one instance of None. If the option holds one elements, it's some(element).
f. Unlike java importing many classes one uses _(underscore) instead of asterisk(*)