kotlin fun main(args : Array<String>) doesn't work in command line

Question

In Kotlin 1.3.30 I just installed, the main entry function doesn't work in command line. JDK is version 8. Intellij Idea is 2019.1.1. No dependency, very clean project.

When I started learning Kotlin, the main entry is 'fun main(args: Array)'. Last year, 'fun main()' could be used without 'args' and I used it a lot. Now I have a project needs command line parameters, but something goes wrong. I've tried 3 formats:

// 1. doesn't work.
fun main(vararg args: String){
    println("this is a test.")
}

// 2. doesn't work
fun main(args: Array<String>){
    println("this is a test.")
}

// 3. this works. but where can I get the command line parameters?
fun main(){
    println("this is a test.")
}

1 & 2 has same response:

λ java -jar test-1.0-SNAPSHOT.jar
Exception in thread "main" java.lang.NoClassDefFoundError: kotlin/jvm/internal/Intrinsics
        at com.yxy.ProgramFileKt.main(ProgramFile.kt)
Caused by: java.lang.ClassNotFoundException: kotlin.jvm.internal.Intrinsics
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        ... 1 more

It works fine with 3 without changing any other thing. But I need command line args.

voddan · Accepted Answer · 2019-04-26 08:57:42Z

3

Judging by the exception, your jar does not contain the Kotlin stdlib. You need to slightly modify your build.

Adding something like this to your Gradle build should fix it:

dependencies {
  compile "org.jetbrains.kotlin:kotlin-stdlib:1.2.0"
}

P.S. This error is very common and has little to do with the main function. Try googling the error message.

answered Apr 26, 2019 at 8:57

voddan

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4 Comments

Roland Over a year ago

... that however wouldn't explain why main without parameters did work... except... there was some stdlib there and now it isn't?

IEE1394 Over a year ago

@Roland it does, if you have a look at Intrinsics (github.com/JetBrains/kotlin/blob/master/libraries/stdlib/jvm/…) there are a lot of checks, which probably skipped it main has no args and therefore main without runs without stdlib

Juan Over a year ago

Most probably once it encountered the Array or String types in the function declaration, it tried to look for it in the stdlib and couldn't find the stdlib.

Jason Over a year ago

Before upgrade to newest IDEA & Kotlin, compile "org.jetbrains.kotlin:kotlin-stdlib-jdk8" is added automatically and everything is fine. But with the newest version, implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8" was added only. Manual add kotlin-stdlib-jdk8 which include stdlib works.

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