MyClass.java

import java.util.List;
import java.util.Arrays;

import org.graalvm.polyglot.*;

public class MyClass {
    public static void main(String[] args) {
        try (Context context = Context.newBuilder().allowAllAccess(true).build()) {

            context.eval("python",
                    "import polyglot\n" + 
                    "@polyglot.export_value\n" + 
                    "def doubleMe(x):\n" + 
                    "  return [a * 2 for a in x]");

            // explore v.as(Function.class) to convert to java.util.Function
            Value doubleMe = context.getBindings("python").getMember("doubleMe");
            List input = Arrays.asList(1, 2, 3); 
            Value result = doubleMe.execute(input);
            List resultAsJavaObject = result.as(List.class);
            System.out.println(resultAsJavaObject); // prints [2, 4, 6]
        }
    }
}