https://medium.com/@alessandroheres/scala-internals-and-intermediates-483e654bb6d2 > In our previous Scala guides, we covered Scala on a very external level; installation, syntax and semantics, debugging and unit testing. In this guide, we aim to explore Scala’s toolchain and internals. > Finally, please ensure that you have installed both Scala and scalac, the language and its compiler respectively. This means you will also need the Java Development Kit (JDK), preferably JDK8. If you require assistance in setting up any of these, you can refer to our Scala installation guide.