http://docs.scala-lang.org/tutorials/tour/tour-of-scala.html

http://www.scala-lang.org/documentation/

http://docs.scala-lang.org/overviews/?_ga=2.8349685.636410797.1498641561-1908126350.1495619268

http://docs.scala-lang.org/overviews/core/futures.html

http://www.scala-lang.org/docu/files/ScalaOverview.pdf

http://www.scala-lang.org/docu/files/ScalaTutorial.pdf

http://www.scala-lang.org/files/archive/spec/2.12/01-lexical-syntax.html

scala study