Scala Introduction for Java developers

doc.md

Scala Introduction for Java developers

• ScalaMatsuri 2017

prerequisites

• JDK 8+ (if you'd like to use the latest Scala)
• brew install sbt to install the global sbt launcher script

scala lang version

You can switch the version when starting the JVM.

• 2.11.x on Java 7
• 2.11.x on Java 8
• 2.12.x on Java 8

Scala lang binary version

Binary compatibilities are not kept between the bin versions.

• 2.9.0
• 2.9.1
• 2.9.2
• 2.10.x
• 2.11.x
• 2.12.x
• 2.13.x

Getting started

• on the REPL: sbt console
• Setup Atom + ENSIME (in Japanese): https://gist.github.com/seratch/cc472f64f72ba725360ee6517008e23c
• IntelliJ IDEA (preparing sbt project and load it)

IntelliJ Setup Demo

# brew install sbt
mkdir -p hello-scala/project
cd hello-scala
echo 'sbt.version=0.13.13' > project/build.properties
echo 'scalaVersion := "2.12.1"' > build.sbt
sbt

Hello World

on the REPL

sbt console
# println("Hello World")

IntelliJ IDEA

• Run
• Debug

object Example extends App {
  println("Hello World!")
}

diff java scala

• package, package object, import renamed package/class/trait
• Immutable Collection, Option
• class, trait, object
• companion object for static things
• test (ScalaTest, specs2)

Test Demo

• http://www.scalatest.org/

echo 'libraryDependencies += "org.scalatest" %% "scalatest" % "3.0.1" % "test"' >> build.sbt

Other Links

• http://skinny-framework.org/
• http://scalikejdbc.org/
• Java エンジニアチームが始めやすい Scala コーディングスタイル: https://www.slideshare.net/seratch/java-scala-ichigayageek