Scala: Lists

Lists

object Lists {
  val emptyList = List()
  val otherEmptyList = Nil

  val items = List("foo", "bar", "baz")
  val consStyleItems = "foo" :: "bar" :: "baz" :: Nil // cons prepend to front of Nil list
  val concatStyleItems = List("foo", "bar") ::: List("baz")

  items(2) // returns 'baz'
  items.count(s => s.length == 3) // counts number of items with length of three chars
  items.drop(2) // drops first two elements and returns rest of list
  items.dropRight(2) // drops RIGHT MOST two elements and returns rest of list
  items.exists(s => s == "bar") // boolean: contains item?
  items.forall(s => s.startsWith("b")) // Boolean: all items start with "b"
  items.forall(s => s.length == 3) // Boolean: all items three chars long
  items.foreach(print)
  items.isEmpty // Boolean
  items.head // first item
  items.init // all but the last item
  items.last // the last item
  items.tail // list minus first element
  items.length // Int

  val extraItems = items ::: List("password", "extra")
  extraItems.filter(s => s.length == 3) // filters only strings with three chars
  extraItems.foreach(s => s.startsWith("b"))
  extraItems.map(s => "x" + s + "x")
  extraItems.map(s => if (s == "password") { "[redacted]" } else { s })
  extraItems.filterNot(s => s.length > 3) // new list without the matching items
  extraItems.mkString(", ") // make a String out of the List
  extraItems.reverse

  extraItems.sortBy(s => s)
}