Kotlin with gradle not working

Support
1

I am trying to initialise a basic Kotlin project using Gradle.
I followed this official doc step by step but I am getting this error

Error: Main method not found in class org.example.MainKt, please define the main method as:
   public static void main(String[] args)
or a JavaFX application class must extend javafx.application.Application

This is my Main.kt file

package org.example

fun main() {
    println("Hello World!")
}

This is the build.gradle.kts file.

plugins {
    kotlin("jvm") version "2.1.10"
}

group = "org.example"
version = "1.0-SNAPSHOT"

repositories {
    mavenCentral()
}

dependencies {
    testImplementation(kotlin("test"))
}

tasks.test {
    useJUnitPlatform()
}
kotlin {
    jvmToolchain(21)
}
2

Showing the gradle file as well would be helpful.

3

Added

4

You shouldn’t need to do this, but try changing your Main.kt file to this:

class Main {
    companion object {
        @JvmStatic
        fun main(args: Array<String>) {
            println("Hello World!")
        }
    }
}
5

Thanks it worked. Is it like java where you need a class with the same name as the file with a static main method? Can you link to documentation, I don’t remember reading that in docs.

6

The class doesn’t need to be the same name as the file, I think. The issue is a static function in a companion object vs a function in a file.

class Main {
    companion object {
        @JvmStatic
        fun main(args: Array<String>) {
            println("Hello World!")
        }
    }
}

The above code is equivalent to the following Java code:

public class Main {
    public static void main(String[] args) {
        System.out.println("Hello World!");
    }
}

As of around Kotlin 1.3 or so, they added the ability to define a main method outside a companion object. So in theory, you can replace that Kotlin code above, with this:

fun main() {
    println("Hello World!")
}

That’s not working for you, and I’m not 100% sure why. But the fix is pretty easy, as I showed you. Hopefully someone who knows more than me can figure out why it doesn’t work if you just put the main method directly in the file. :slightly_smiling_face:

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