Scala - IntelliJ IDEA Error: Could not find or load main class

Question

I am currently using IntelliJ IDEA 2018.3.4 which I am trying to integrate with Scala but to no avail.

I have installed the Scala and SBT plugins and used the following steps in creating my project:

File > Create New Project
Selected Java from the left
Selected Scala from the right > Next
Entered the name of the project > FINISH

From there, the project is created. Following other guides, I then:

Right click on the src directory
New > File
Enter main/scala/Main.scala
And enter the following code in there:

Code:

package main.scala

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

But after right clicking in the editor and selecting Run Main, I get the following message:

Error: Could not find or load main class

Has anyone experienced this or can provide any solution?

Note

I have also tried creating a Scala application with sbt but the syncing process for the sbt dump never ends or gives an error and when I run the project, I get the same error.

Seems like it would make more sense to select a Scala project in step 1, rather than a Java project with Scala support...? — jwismar, Feb 22 '19 at 14:40
@jwismar Sorry, just updated my question. I tried that (Scala with sbt) but the syncing process remains ongoing (never ends or fails) and when I run the code I get the same error. — Omari Celestine, Feb 22 '19 at 14:43
Sorry to tell you, I followed the steps above except created a Scala project with SBT. I was not able to reproduce the problem. It printed "Hello World" and terminated normally. — jwismar, Feb 22 '19 at 14:45
Follow this tutorial: http://allaboutscala.com/tutorials/chapter-1-getting-familiar-intellij-ide/where-is-main-method-launch-scala-application/ You name eerything main, which I think is not very clever to do. — Dilyano Senders, Feb 22 '19 at 14:45
@DilyanoSenders I recently followed that and I have tried different names for the object file but same result. — Omari Celestine, Feb 22 '19 at 14:48
That's correct. Only the change in project type. Otherwise cut-and-pasted your code snippet. I also double-checked that I'm using the same version of IntelliJ as you are. — jwismar, Feb 22 '19 at 14:49
Could you go to the "build" menu and choose for "Rebuild Project" — Dilyano Senders, Feb 22 '19 at 14:57
Looks like I'm using sbt 1.1.6. And I'm on a Mac, if that's relevant. — jwismar, Feb 22 '19 at 14:59
@OmariCelestine check [idea.log](https://intellij-support.jetbrains.com/hc/articles/207241085) for errors. See also https://stackoverflow.com/a/42660624/104891. — CrazyCoder, Feb 22 '19 at 20:10

score 1 · Answer 1 · answered Feb 22 '19 at 14:45

1

For Intellj IDEA, probably you will need to double check your module settings, and see if your scala folder is marked as sources root.

Check this URL for more details: https://www.jetbrains.com/help/idea/creating-and-managing-modules.html

answered Feb 22 '19 at 14:45

Vinh Truong

388
1
10

score 1 · Answer 2 · answered Oct 26 '20 at 17:38

When I experienced this issue after recreating your situation almost exactly step-by-step, what fixed the problem was putting the scala file, in your case Main.scala, in another package, named anything you want it to be, inside main/scala. Ultimately, the scala file's path would be something like

main/scala/<package-name>/Main.scala

Then, after fixing the package name in the scala file and running the scala file through IntelliJ, everything worked as it was supposed to.

Scala - IntelliJ IDEA Error: Could not find or load main class

2 Answers2