It seems as though Eclipse has abandoned Scala for now, so I recommend switching to IntelliJ.
1. Download IntelliJ IDEA the EDU version.
2. Install the latest Scala Plugin to IntelliJ.
3. Download Java 8, 11, or 17 (when it's available) from http://adoptopenjdk.net, not from Oracle. For more info see:
· http://horstmann.com/unblog/2018-10-04/index.html
· http://horstmann.com/unblog/2018-09-17/index.html
4. When creating a new Scala project I select New Project from the File menu. I select Scala from the New Project dialog. Following IntelliJ's recommendation, I select sbt as the build tool for the project.
5. Scala has several execution modes: repl, worksheet, and app.
5.1 REPL (read-execute-print loop) is the Scala interpreter. If you don't see "repl" under the tools menu, then click the "Add Configurations" button in the upper right. Select Scala REPL from the templates list and click OK.
5.2 To create a worksheet, right click the source node in the project view on the left. Under "New" you should see "Scala Worksheet". You will be prompted for a name. If you call it "Demo" for example, a file named Demo.sc will be created.
5.3 To create an app, right click the scala folder under main under src in the project folder. Under New in the drop-down menu select "Scala class". In the dialog box select object and specify a name. I If you call it "Demo" for example, a file named Demo.scala will be created. Add "extends App" to the declaration of the Demo object in this file:
object Demo extends App { }