Scala 2.8 HelloWorld Program ClassNotFoundException - scala

Question

I'm trying to run a scala program,
class HelloWorld {
var myField = 0;
def getMyField() : Int = {
return this.myField;
}
}
I keep getting a ClassNotFoundException even though the program is named HelloWorld.scala
Full Error below
Exception in thread "main" java.lang.ClassNotFoundException: HelloWorld
at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:190)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:122)
Okay, looking at the documentation of scala http://www.scala-lang.org/documentation/getting-started.html
I changed the code to this,
object HelloWorld {
def main(args: Array[String]) {
println("Hello, world!")
}
}
This is the error now
Information:24/7/15 10:55 AM - Compilation completed with 1 error and 7 warnings in 2s 32ms
Error:scalac: Error: org.jetbrains.jps.incremental.scala.remote.ServerException
Error compiling sbt component 'compiler-interface-2.8.0.final-51.0'
at sbt.compiler.AnalyzingCompiler$$anonfun$compileSources$1$$anonfun$apply$2.apply(AnalyzingCompiler.scala:145)
at sbt.compiler.AnalyzingCompiler$$anonfun$compileSources$1$$anonfun$apply$2.apply(AnalyzingCompiler.scala:142)
at sbt.IO$.withTemporaryDirectory(IO.scala:285)
at sbt.compiler.AnalyzingCompiler$$anonfun$compileSources$1.apply(AnalyzingCompiler.scala:142)
at sbt.compiler.AnalyzingCompiler$$anonfun$compileSources$1.apply(AnalyzingCompiler.scala:139)
at sbt.IO$.withTemporaryDirectory(IO.scala:285)
at sbt.compiler.AnalyzingCompiler$.compileSources(AnalyzingCompiler.scala:139)
at sbt.compiler.IC$.compileInterfaceJar(IncrementalCompiler.scala:33)
at org.jetbrains.jps.incremental.scala.local.CompilerFactoryImpl$.org$jetbrains$jps$incremental$scala$local$CompilerFactoryImpl$$getOrCompileInterfaceJar(CompilerFactoryImpl.scala:87)
at org.jetbrains.jps.incremental.scala.local.CompilerFactoryImpl$$anonfun$getScalac$1.apply(CompilerFactoryImpl.scala:44)
at org.jetbrains.jps.incremental.scala.local.CompilerFactoryImpl$$anonfun$getScalac$1.apply(CompilerFactoryImpl.scala:43)
at scala.Option.map(Option.scala:145)
at org.jetbrains.jps.incremental.scala.local.CompilerFactoryImpl.getScalac(CompilerFactoryImpl.scala:43)
at org.jetbrains.jps.incremental.scala.local.CompilerFactoryImpl.createCompiler(CompilerFactoryImpl.scala:22)
at org.jetbrains.jps.incremental.scala.local.CachingFactory$$anonfun$createCompiler$1.apply(CachingFactory.scala:24)
at org.jetbrains.jps.incremental.scala.local.CachingFactory$$anonfun$createCompiler$1.apply(CachingFactory.scala:24)
at org.jetbrains.jps.incremental.scala.local.Cache$$anonfun$getOrUpdate$2.apply(Cache.scala:20)
at scala.Option.getOrElse(Option.scala:120)
at org.jetbrains.jps.incremental.scala.local.Cache.getOrUpdate(Cache.scala:19)
at org.jetbrains.jps.incremental.scala.local.CachingFactory.createCompiler(CachingFactory.scala:23)
at org.jetbrains.jps.incremental.scala.local.LocalServer.compile(LocalServer.scala:22)
at org.jetbrains.jps.incremental.scala.remote.Main$.make(Main.scala:62)
at org.jetbrains.jps.incremental.scala.remote.Main$.nailMain(Main.scala:20)
at org.jetbrains.jps.incremental.scala.remote.Main.nailMain(Main.scala)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.martiansoftware.nailgun.NGSession.run(NGSession.java:319)
Warning:scalac: /tmp/sbt_20e2573f/compiler-interface-sources/CompilerInterface.scala:161: error: object creation impossible, since method registerTopLevelSym in trait GlobalCompat of type (sym: this.Symbol)Unit is not defined
Warning:scalac: new Compiler() with RangePositions // unnecessary in 2.11
Warning:scalac: ^
Warning:scalac: /tmp/sbt_20e2573f/compiler-interface-sources/CompilerInterface.scala:165: error: class Compiler needs to be abstract, since method registerTopLevelSym in trait GlobalCompat of type (sym: Compiler.this.Symbol)Unit is not defined
Warning:scalac: class Compiler extends CallbackGlobal(command.settings, dreporter, output)
Warning:scalac: ^
Warning:scalac: two errors found

Answer 1

Your errors are not in the code but in the way you're trying to run the code.
I loaded the code into the REPL and got no error. I loaded the code into IntelliJ and got lots of style warnings but no errors. I compiled the code and ran it from the command line:
%> java HelloWorld
Error: Main method not found in class HelloWorld, please define the
main method as:
public static void main(String[] args)
Which is what one should expect.

Answer 2

I am not getting how you are trying to run your program. Since I am not getting any errors. Let me share you a simple way to run your code snippet.
class HelloWorld{
var myField = 0;
def getMyField() : Int = {
return this.myField;
}
}
object Test extends App{
println(new HelloWorld().getMyField())
}
Try to run Test object by right clicking inside Test. Hope I was helpful.

Answer 3

Assuming you are running IntelliJ, try to build the project (CTRL+F9) and then run it. I had the same issue and it worked for me.