Error in running Scala Program: Main method not found in class main, please define the main method

Question

I am totally new in Scala. What I have done is that, I have installed Scala 2.13.6 , SBT 1.5.5 and Intellij 2021.2 on Ubuntu 20.04. I have installed plugin scala and sbt executor in Intellij. When I create a new Scala class and write this code to it, I can run that without any errors:

object main extends App{
    println("Hello")
}

But when I have this code, I cannot run it:

class exm {
   def main(args: Array[String]): Unit={
    println("Hello world")
      }
}

The error is in the following:

Error: Main method is not static in class exm, please define the main method as:public static void main(String[] args)

I know that IDE think the code is Java, but why?

Any help would be really appreciated.

Answer 1

The main function needs to be inside an object, not a class definition. So instead of this

package main_function_test

class exm {
  def main(args: Array[String]): Unit = {
    println("Hello world")
  }
}

write this:

package main_function_test

object exm {
  def main(args: Array[String]): Unit = {
    println("Hello world")
  }
}