brew install sbt@1
Try the "Hello, World" example from scala-lang.org:
object HelloWorld {
def main(args: Array[String]): Unit = {
println("Hello, world!")
}
}
Run it:
Go [15:46: learning-scala$] sbt run [warn] No sbt.version set in project/build.properties, base directory:~alt/learning-scala [info] Set current project to learning-scala (in build file:~/alt/learning-scala/) [info] Compiling 1 Scala source to ~/alt/learning-scala/target/scala-2.12/classes ...
[info] Non-compiled module 'compiler-bridge_2.12' for Scala 2.12.4. Compiling... [info] Compilation completed in 11.024s. [info] Done compiling. WARNING: An illegal reflective access operation has occurred WARNING: Illegal reflective access by com.google.protobuf.UnsafeUtil (file:~/.sbt/boot/scala-2.12.4/org.scala-sbt/sbt/1.1.0/protobuf-java-3.3.1.jar) to field java.nio.Buffer.address WARNING: Please consider reporting this to the maintainers of com.google.protobuf.UnsafeUtil WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations WARNING: All illegal access operations will be denied in a future release [info] Packaging ~/alt/learning-scala/target/scala-2.12/learning-scala_2.12-0.1.0-SNAPSHOT.jar ... [info] Done packaging. [info] Running HelloWorld Hello, world! [success] Total time: 16 s, completed 9 Feb 2018, 15:47:03
Well, it worked. But that's a helluva lot of warnings for very little code!
A colleague informs me how to set up another Hello World that's known to work:
sbt new https://github.com/scala/scala-seed.g8
(enter name: hello)
cd hello
sbt run
...but I still get the warnings, although the code does output "hello" as expected.
WARNING: An illegal reflective access operation has occurred WARNING: Illegal reflective access by com.google.protobuf.UnsafeUtil (file:~/.sbt/boot/scala-2.12.4/org.scala-sbt/sbt/1.1.0/protobuf-java-3.3.1.jar) to field java.nio.Buffer.address WARNING: Please consider reporting this to the maintainers of com.google.protobuf.UnsafeUtil
It seems I've just joined Scala at a time when 1.0 has recently been released, and lots of existing code does not exactly make the compiler happy yet.
Note: The warning was not displayed the second time I ran the program. Somehow it remembers.
To do:
- Find out how to avoid the warning.
- Find out how to repeat the warning!
Posts
