works

.gitignore

@@ -2,3 +2,4 @@ minmax-java/build
 minmax-java/.gradle
 .idea
 target
+*.so

README.md

@@ -0,0 +1,23 @@
+# Minmax in Rust with JNI
+
+## How to build and run
+
+### Prerequisites
+- Gradle
+- Rust toolchain
+
+### Compile Rust code
+
+`cargo build`
+
+### Assemble shared library
+
+Copy the shared library in `target/debug/librs_wrapper.so` (or a `.dll` on windows) to a known location like the working directory or the system wide library directory.
+
+### Build the jar
+
+Use `./gradlew jar` or whatever you like I don't know.
+
+### Run the program
+
+Maybe it works now. If you get a link error you might need to set the `LD_LIBRARY_PATH` env var to the path of the shared library (on linux). Or you have to copy it to the systems library directory. Or something else. But it should work.

minmax-java/build.gradle

@@ -11,6 +11,12 @@ java {
 	}
 }
 
+jar {
+    manifest {
+        attributes 'Main-Class': 'ch.bbw.m411.connect4.Connect4ArenaMain'
+    }
+}
+
 repositories {
 	mavenCentral()
 }

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) {