scala programming language & List

recommend book : Programming in Scala 2nd
Source code : http://booksites.artima.com/programming_in_scala_2ed
http://booksites.artima.com/programming_in_scala_2ed/examples/
scala development tool :  http://scala-ide.org/  or  https://www.jetbrains.com/idea/
http://www.scala-lang.org/download/
http://www.scala-lang.org/api/2.11.6/#package

create scala file and compile run guide :
https://bcomposes.wordpress.com/2011/10/25/first-steps-in-scala-for-beginning-programmers-part-10/

Eric Raymond introduced the cathedral and bazaar as two metaphors of software
development
reference : The Cathedral and the Bazaar : http://www.unterstein.net/su/docs/CathBaz.pdf

Table 3.1 · Some List methods and usages
What it is           What it does
List() or Nil    :     The empty List
List("Cool", "tools", "rule")
 : Creates a new List[String] with the three values "Cool", "tools", and "rule"
val thrill = "Will" :: "fill" ::"until" :: Nil
 : Creates a new List[String] with the three values "Will", "fill", and "until"
List("a", "b") ::: List("c", "d")
 : Concatenates two lists (returns a new List[String] with values "a", "b", "c", and "d")
thrill(2)
 : Returns the element at index 2 (zero based) of the thrill list (returns "until")
thrill.count(s => s.length == 4)
 : Counts the number of string elements in thrill that have length 4 (returns 2)
thrill.drop(2)
 : Returns the thrill list without its first 2 elements (returns List("until"))
thrill.dropRight(2)
 : Returns the thrill list without its rightmost 2 elements (returns List("Will"))
thrill.exists(s => s == "until")
 : Determines whether a string element exists in thrill that has the value "until" (returns true)
thrill.filter(s => s.length == 4)
 : Returns a list of all elements, in order, of the thrill list that have length 4 (returns
List("Will", "fill"))
thrill.forall(s => s.endsWith("l"))
 : Indicates whether all elements in the thrill list end with the letter "l" (returns true)
thrill.foreach(s => print(s))
 : Executes the print statement on each of the strings in the thrill list (prints "Willfilluntil")
thrill.foreach(print)
 : Same as the previous, but more concise (also prints "Willfilluntil")
thrill.head
 : Returns the first element in the thrill list (returns "Will")
thrill.init
 : Returns a list of all but the last element in the thrill list (returns List("Will", "fill"))
thrill.isEmpty
 : Indicates whether the thrill list is empty (returns false)
 thrill.last
 : Returns the last element in the thrill list (returns "until")
thrill.length
 : Returns the number of elements in the thrill list (returns 3)
 thrill.map(s => s + "y")
 : Returns a list resulting from adding a "y" to each string element in the thrill list
 (returns List("Willy", "filly", "untily"))
 thrill.mkString(", ")
 : Makes a string with the elements of the list (returns "Will, fill, until")
thrill.remove(s => s.length == 4)
 : Returns a list of all elements, in order, of the thrill list except those that have
 length 4 (returns List("until"))
thrill.reverse
 : Returns a list containing all elements of the thrill list in reverse order (returns  List("until", "fill", "Will"))
thrill.sort((s, t) => s.charAt(0).toLower < t.charAt(0).toLower)
 : Returns a list containing all elements of the thrill list in alphabetical order of
 the first character lowercased (returns List("fill", "until", "Will"))
thrill.tail
 : Returns the thrill list minus its first element (returns List("fill", "until"))

reference by : Programming in Scala