convert.scala

val hundred = "100"
println(hundred, hundred.getClass)
println(hundred.toInt, hundred.toInt.getClass)
println(hundred.toDouble, hundred.toDouble.getClass)
println(hundred.toFloat, hundred.toFloat.getClass)
val one = "1"
println(one, one.getClass)
println(one.toInt, one.toLong.getClass)
println(one.toShort, one.toShort.getClass)
println(one.toByte, one.toByte.getClass)

val aString = "hoge"
// not required to declare "throws NumberFormatException"
def toInt(s: String):Option[Int] = {
  try {
    Some(s.toInt)
  } catch {
    case e: NumberFormatException => None
  }
}
toInt(aString) match {
  case Some(n) => println(n)
  case None => println("Boom! That wasn't a number.")
}
// assign the result to x
val x = toInt(aString)
println(toInt("1").getOrElse(0)) // 1
println(toInt("a").getOrElse(0)) // 0