Blog Scala Monad http://blog.joecwu.com/2015/07/scava-scala-monad.html

blog-Scala-Monad-1.scala

val a : Option[String] = Some("abc")

if(a.isEmpty)
  println("do something if a has value "+a.get)
else
  println("do something if a is empty")

blog-Scala-Monad-2.scala

val a : Option[String] = Some("abc")

a.map(v=>println("do someting if a has value "+v)).getOrElse("do something if a is empty")

val b = Option[Int] = a.map{ v =>
  if(v=="abc") 123 else 456
}

val c = Option[Int] = a.flatMap{ v =>
  if(v=="abc") Some(123) else None
}

blog-Scala-Monad-3.scala

def getFutureString() : Future[String] = Future{ Thread.sleep(3000); "abc" }

val str = getFutureString()
// str: scala.concurrent.Future[String]

str.map{ s=> println("I got "+s) }
// res: scala.concurrent.Future[Unit]

// after 3 seconds...

// I got abc