[2.x] Recipe for hello world

src/reference/SUMMARY.md

@@ -21,5 +21,7 @@
   - [Caching](concepts/caching.md)
 - [Reference]()
   - [Remote cache setup](reference/remote-cache-setup.md)
+- [Recipes]()
+  - [Write hello world](recipes/hello-world.md)
 - [Appendix]()
   - [Setup notes](setup-notes.md)

src/reference/recipes/hello-world.md

@@ -0,0 +1,42 @@
+How to write hello world
+========================
+
+Problem
+-------
+
+I want to write a hello world program in Scala, and run it.
+
+Steps
+-----
+
+1. Create a fresh directory, like `hello_scala/`
+2. Create a directory named `project/` under `hello_scala/`, and create `project/build.properties` with
+   ```
+   sbt.version={{sbt_version}}
+   ```
+3. Under `hello_scala/`, create `build.sbt`:
+   ```scala
+   scalaVersion := "{{scala3_example_version}}"
+   ```
+4. Under `hello_scala/`, create `Hello.scala`:
+   ```scala
+    @main def main(args: String*): Unit =
+      println(s"Hello ${args.mkString}")
+   ```
+5. Navigate to `hello_scala/` from the terminal, and run `sbt`:
+   ```bash
+   $ sbt
+   ```
+6. When the prompt appears, type `run`:
+   ```scala
+   sbt:hello_scala> run
+   ```
+7. Type `exit` to exit the sbt shell:
+   ```scala
+   sbt:hello_scala> exit
+   ```
+
+Alternatives
+------------
+
+When you're in a hurry, you can run `sbt init` in a fresh directory, and select the first template.