command line arguments - Scala Args Parsing -


why does

println("hello, " + args(0) + "!")

work when run scala nomain.scala but

object helloworld {   def main(args: list[string]) {     println("hello, " + args(0) + "!")   } }

gives me error:

java.lang.nosuchmethodexception: main.main([ljava.lang.string;)     @ java.lang.class.getmethod(class.java:1786)     @ scala.reflect.internal.util.scalaclassloader.run(scalaclassloader.scala:94)     @ scala.reflect.internal.util.scalaclassloader.run$(scalaclassloader.scala:90)     @ scala.reflect.internal.util.scalaclassloader$urlclassloader.run(scalaclassloader.scala:129)     @ scala.tools.nsc.commonrunner.run(objectrunner.scala:22)     @ scala.tools.nsc.commonrunner.run$(objectrunner.scala:21)     @ scala.tools.nsc.objectrunner$.run(objectrunner.scala:39)     @ scala.tools.nsc.commonrunner.runandcatch(objectrunner.scala:29)     @ scala.tools.nsc.commonrunner.runandcatch$(objectrunner.scala:28)     @ scala.tools.nsc.objectrunner$.runandcatch(objectrunner.scala:39)     @ scala.tools.nsc.scriptrunner.runcompiled(scriptrunner.scala:170)     @ scala.tools.nsc.scriptrunner.$anonfun$runscript$1(scriptrunner.scala:187)     @ scala.tools.nsc.scriptrunner.$anonfun$runscript$1$adapted(scriptrunner.scala:187)     @ scala.tools.nsc.scriptrunner.$anonfun$withcompiledscript$2(scriptrunner.scala:156)     @ scala.tools.nsc.scriptrunner.runscript(scriptrunner.scala:124)     @ scala.tools.nsc.scriptrunner.runscriptandcatch(scriptrunner.scala:200)     @ scala.tools.nsc.maingenericrunner.runtarget$1(maingenericrunner.scala:63)     @ scala.tools.nsc.maingenericrunner.run$1(maingenericrunner.scala:88)     @ scala.tools.nsc.maingenericrunner.process(maingenericrunner.scala:99)     @ scala.tools.nsc.maingenericrunner$.main(maingenericrunner.scala:104)     @ scala.tools.nsc.maingenericrunner.main(maingenericrunner.scala)

when run scala helloworld.scala

i tried adding statements if (args.size > 0) gives me errors. wondering doing wrong here. wondering how check see if list has in , how directly print args.

def main(args: array[string]): unit = ???

should instead of

def main(args: list[string]): unit = ???

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