Example on jbang enabling graalvm -truffle / espresso feature

HotSwapDemo.java

///usr/bin/env jbang "$0" "$@" ; exit $?
//JAVA_OPTIONS -truffle

//`-truffle` is there to enable graalvm espresso. 
// See https://medium.com/graalvm/java-on-truffle-going-fully-metacircular-215531e3f840
// with sdman you can do the following to install:
// sdk install java 21.0.0.r11-grl
// gu install espresso
// gu install native-image  ## optional

import java.util.Random;


public class HotSwapDemo {

    private static final int ITERATIONS = 100;

    public static void main(String[] args) {
        HotSwapDemo demo = new HotSwapDemo();
        System.out.println("Starting HotSwap demo with Java on Truffle");
        // run something in a loop
        for (int i = 1; i < ITERATIONS; i++) {
            demo.runDemo(i);
        }
        System.out.println("Completed HotSwap demo with Java on Truffle");
    }

    public void runDemo(int iteration) {
        int random = new Random().nextInt(iteration);
        System.out.printf("\titeration %d ran with result: %d\n", iteration, random);
    }
}