warning: Kotlin runtime JAR files in the classpath should have the same version

Question or issue of Kotlin Programming:

I get the following warning, but I’m not sure where v1.0.6 resides.

Is it possible this error comes from a Kotlin library somehow including an old Kotlin version?

Any ideas how to fix it or at least how can I follow the suggestion to make kotlin-reflect explicit (1.1) ?

How to solve this issue?

Solution no. 1:

It seems that your project is configured in such a way that you depend on kotlin-stdlib 1.1 and kotlin-reflect 1.0. The most likely case is that you already have an explicit dependency on kotlin-stdlib 1.1 but have no dependency on kotlin-reflect, and some other library (which you depend on) depends on kotlin-reflect 1.0.

If that indeed is the case, the solution is to provide an explicit dependency on kotlin-reflect 1.1.

In Maven, add this to pom.xml:

    
        
            org.jetbrains.kotlin
            kotlin-reflect
            1.1.0
        
    

In Gradle, add this to build.gradle:

dependencies {
    implementation "org.jetbrains.kotlin:kotlin-reflect:1.1.0"
}

See some info about this and related warnings in the official docs.

Solution no. 2:

I fixed warning by overwriting kotlin version used in my app

configurations.all {
    resolutionStrategy.eachDependency { DependencyResolveDetails details ->
        def requested = details.requested
        if (requested.group == 'org.jetbrains.kotlin' && requested.name == 'kotlin-reflect') {
            details.useVersion kotlin_version
        }
    }
}

e.g. kotlin_version = 1.3.0

Solution no. 3:

firstly, figure out the reason by the gradle script below

./gradlew app:dependencies

(change app to your gradle module name)

+--- project :common
|    +--- org.jetbrains.kotlin:kotlin-stdlib:1.3.61
|    |    +--- org.jetbrains.kotlin:kotlin-stdlib-common:1.3.61
|    |    \--- org.jetbrains:annotations:13.0
|    +--- org.jetbrains.kotlinx:kotlinx-coroutines-core-common:1.3.3
|    |    \--- org.jetbrains.kotlin:kotlin-stdlib-common:1.3.61
|    +--- org.jetbrains.kotlinx:kotlinx-serialization-runtime-common:0.12.0 -> 0.14.0
|    |    \--- org.jetbrains.kotlin:kotlin-stdlib-common:1.3.60 -> 1.3.61

Then, the dependency tree will be shown.
check which dependency use the issue dependency.

If you found the dependency, decide how to solve it.

1. upgrade the dependency’s version(the dependency’s latest version may refer to latest issue dependency’s version)
2. or exclude the issue dependency from the dependency
3. or follow other answers.

I’m not sure what is the best way. kindly just refer to it.

Solution no. 4:

it happens when you are using the dagger in a kotlin project(android) and you have the kotlin version to be 1.7 i.e

implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"

all you have to do is add the dependency below to your app build gradle level

  implementation "org.jetbrains.kotlin:kotlin-reflect:1.3.50"

Solution no. 5:

Make sure you use the same version of stdlib-jdk7 & kotlin-gradle-plugin dependencies to avoid warnings.
You can refere below example where stdlib-jdk7 & kotlin-gradle-plugin both have the same version

app-level build.gradle file

dependencies { implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:1.4.0" ... } 

project-level build.gradle file

buildscript { dependencies { classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:1.4.0" ... } 

}

Hope this helps!