works

minmax-java/build.gradle

@@ -11,6 +11,12 @@ java {
 	}
 }
 
+jar {
+    manifest {
+        attributes 'Main-Class': 'ch.bbw.m411.connect4.Connect4ArenaMain'
+    }
+}
+
 repositories {
 	mavenCentral()
 }
@@ -23,4 +29,4 @@ dependencies {
 
 tasks.named('test') {
 	useJUnitPlatform()
-}
+}

minmax-java/src/main/java/ch/bbw/m411/connect4/RustPlayer.java

@@ -3,6 +3,13 @@ package ch.bbw.m411.connect4;
 public class RustPlayer extends Connect4ArenaMain.DefaultPlayer {
     private static native int rustPlay(byte player, byte[] board);
 
+    static {
+        // This actually loads the shared object that we'll be creating.
+        // The actual location of the .so or .dll may differ based on your
+        // platform.
+        System.loadLibrary("rs_wrapper");
+    }
+
     @Override
     protected int play() {
         byte player = switch (this.myColor) {