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I’m trying to stay as simple (less tools) as possible, working only at command line with vi and a few files.

ShowVersions.java

import org.opencv.core.Core;

public class ShowVersions {

  static {
    System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
  }

  public static void main(String[] args) {
    System.out.println("Hello OpenCV " + Core.VERSION + "!");
    System.out.println("Hello to you too, Java " + System.getProperty("java.version") + "!");
  }
}

Compiled with:

javac -cp /usr/share/java/opencv4/opencv-410.jar ShowVersions.java

Executed with:

java -Djava.library.path=/usr/lib -cp /usr/share/java/opencv4/opencv-410.jar:. ShowVersions

The output:

Hello OpenCV 4.1.0!
Hello to you too, Java 12.0.1!

But, trying with Kotlin...

ShowVersions.kt

import org.opencv.core.Core

fun main(args: Array<String>) {
  System.loadLibrary(Core.NATIVE_LIBRARY_NAME)
  println("Hello OpenCV " + Core.VERSION + "!")
  println("Hello to you too, Java " + System.getProperty("java.version") + "!")
}

Compiled with:

kotlinc ShowVersions.kt -classpath /usr/share/java/opencv4/opencv-410.jar -include-runtime -d ShowVersions.jar

Executed with:

java -Djava.library.path=/usr/lib -cp /usr/share/java/opencv4/opencv-410.jar:. -jar ShowVersions.jar

No sucess...

Exception in thread "main" java.lang.NoClassDefFoundError: org/opencv/core/Core
        at ShowVersionsKt.main(ShowVersions.kt:5)
Caused by: java.lang.ClassNotFoundException: org.opencv.core.Core
        at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:583)
        at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178)
        at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521)
        ... 1 more

:( What do I need to do to get this simple test code to work in Kotlin as easy as was in Java?