Kotlin Error 'unresolved reference' appears when trying to run Java Code from a Kotlin file

Question

Referencing Problem when Java Class is used in Kotlin. There is the Java class Base32Decoder.java and code from this class is used in the Kotlin file hello.kt.

When I try to run Java code through a Kotlin file, an error occurs because of no reference could be established to the Java class Base32Decoder.

Error message:

hello.kt:4:25: error: unresolved reference: Base32Decoder

Base32Decoder Java class can't resolve the reference to it. Since this class is used inside the Kotlin file, the reference needs to work.

Code

fun main(args: Array<String>){
    val Base32Decoder = Base32Decoder()
   val rectangleArea: String = Base32Decoder.base32Decode("JBSWY3DPFQQFO33SNRSCC===")
   println("inside the Kotlin codes:" + rectangleArea)
}

How can I reference Java classes when I want to use Java code in Kotlin files?

Please provide enough code so others can better understand or reproduce the problem. — Lore, Jun 01 '23 at 14:31
Have you added the library to the classpath, and have you added the appropriate import in your Kotlin source file? — Mark Rotteveel, Jun 02 '23 at 08:47

score 1 · Accepted Answer · edited Jun 02 '23 at 08:49

1

The code must be accessible for Kotlin. This means you have to compile (If you compile code in terminal: javac SampleFile.java The Base32Decoder.java file to generate the Base32Decoder.class.

Now generate the JAR-file with a link to the Kotlin file in command line:

jar cf app.jar Base32Decoder.class hello.kt

Now since you use kotlinc you can execute the code in command line like this:

kotlinc -classpath app.jar -script hello.kt

Now your code should run fine. The problem is that Kotlin didn't have access to the Base32Decoder.java class.

edited Jun 02 '23 at 08:49

Mark Rotteveel

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answered Jun 01 '23 at 13:54

AztecCodes

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@aztecodes in this way there is an error error: unresolved reference: base32Decode – EpicAdidash Jun 01 '23 at 15:24
@EpicAdidash Could you please add the code from your hello.kt Kotlin file? Also do you use an IDE or do you work with Terminal? – AztecCodes Jun 01 '23 at 15:56
I use terminal for working – EpicAdidash Jun 01 '23 at 16:03
@EpicAdidash And when you follow my answer you get this error? – AztecCodes Jun 01 '23 at 16:04
Yes , This happened after trying your solution – EpicAdidash Jun 01 '23 at 16:05
@EpicAdidash Could you please add the whole code of the Kotlin file? – AztecCodes Jun 01 '23 at 16:05
I added it right now – EpicAdidash Jun 01 '23 at 16:06
Let us [continue this discussion in chat](https://chat.stackoverflow.com/rooms/253919/discussion-between-azteccodes-and-epicadidash). – AztecCodes Jun 01 '23 at 16:07

Kotlin Error 'unresolved reference' appears when trying to run Java Code from a Kotlin file

1 Answers1