Scala - Console (Interactive Shell|REPL)

With Scala

scala

Welcome to Scala version 2.11.7 (Java HotSpot(TM) 64-Bit Server VM, Java 1.7.0_79).
Type in expressions to have them evaluated.
Type :help for more information.

scala> object HelloWorld {
     |   def main(args: Array[String]): Unit = {
     |     println("Hello, world!")
     |   }
     | }

defined object HelloWorld

scala> HelloWorld.main(Array())

Hello, world!

With sbt

Scala - SBT (Builder)

sbt console