Question

This one should be simple, but I can’t figure it out myself.

I have Scala 2.9.1 installed on an Ubuntu 12.04 system.

The file is helloworld.scala:

object HelloWorld{
        def main(args:Array[String]){
                println("Hello, World!")
        }
}

scalac helloworld works totally fine without issue. Then scala HelloWorld gives

Exception in thread "main" java.lang.RuntimeException: Cannot figure out how to run target: HelloWorld
    at scala.sys.package$.error(package.scala:27)
    at scala.tools.nsc.GenericRunnerCommand.scala$tools$nsc$GenericRunnerCommand$$guessHowToRun(GenericRunnerCommand.scala:38)
    at scala.tools.nsc.GenericRunnerCommand$$anonfun$2.apply(GenericRunnerCommand.scala:48)
    at scala.tools.nsc.GenericRunnerCommand$$anonfun$2.apply(GenericRunnerCommand.scala:48)
    at scala.Option.getOrElse(Option.scala:108)
    at scala.tools.nsc.GenericRunnerCommand.<init>(GenericRunnerCommand.scala:48)
    at scala.tools.nsc.GenericRunnerCommand.<init>(GenericRunnerCommand.scala:17)
    at scala.tools.nsc.MainGenericRunner.process(MainGenericRunner.scala:33)
    at scala.tools.nsc.MainGenericRunner$.main(MainGenericRunner.scala:89)
    at scala.tools.nsc.MainGenericRunner.main(MainGenericRunner.scala)

I’ve seen this question several times on forums but the poster is usually just mixing the class name and the file name so they would be trying scala helloworld, this is not what I’m doing (right?) but I get the same error.

Edit

scala -classpath ./ HelloWorld works fine. So it’s a classpath problem.

Answer 1

I tried this and got exactly the same. Then I cleared my classpath thus:

$ CLASSPATH=

and all worked.