IntelliJ IDEA for Scala Development

Download the Scala archive file from http://www.scala-lang.org/download/ and uncompress it.

Creating a simple Scala project

Set Scala home to the directory (e.g. ~/scala-2.11.0/).

Using the Scala console

Right click a Scala item (e.g. file, class name), pick Run Scala Console.... Press Ctrl + Enter to evaluate the expression.

scala> 1+2
res1: Int = 3

Creating a Scala project with Maven

Show type information for Scala expressions

Press Alt + =. (source)