Kotlin Application with Gradle application plugin - gradle

Question

I am trying to create a simple HelloWorld application using kotlin, gradle, and the gradle application plugin. When I run it with the below setup I get the following error:
Error: Main method is not static in class com.petarkolaric.helloworld.Main, please define the main method as:
public static void main(String[] args)
My build.gradle:
group 'helloworld'
version '1.0-SNAPSHOT'
buildscript {
ext.kotlin_version = '1.2.0'
repositories {
mavenCentral()
}
dependencies {
classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
}
}
apply plugin: 'kotlin'
apply plugin: 'application'
mainClassName = "com.petarkolaric.helloworld.Main"
repositories {
mavenCentral()
}
dependencies {
compile "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
}
compileKotlin {
kotlinOptions.jvmTarget = "1.8"
}
compileTestKotlin {
kotlinOptions.jvmTarget = "1.8"
}
My src/main/kotlin/com/petarkolaric/helloworld/Main.kt:
package com.petarkolaric.helloworld
class Main {
fun main(args : Array<String>) {
println("Hello, World!")
}
}
According to this blog post I should be able to use the application plugin this way.
What do I need to change to allow the application plugin to run my main function when I run gradle run?

Answer 1

As the error says, your main method is not static. You have the following options:
1) Put the main into the companion object and make it JvmStatic
class Main {
companion object {
#JvmStatic
fun main(args : Array<String>) {
println("Hello, World!")
}
}
}
2) Change your class to object - than you more or less have a singleton class and make it JvmStatic
object Main {
#JvmStatic
fun main(args : Array<String>) {
println("Hello, World!")
}
}
3) Place the main outside the class
fun main(args : Array<String>) {
println("Hello, World!")
}
class Main {
}