Native image is experimental, and I believe is a separate download now. Maybe someone from the Graal team can give more precise information about what exactly works in stock OpenJDK, but you should try that demo with Java 12 (or even 13). While you're at it, also give ZGC a try (see https://news.ycombinator.com/item?id=19886856 and http://www.programmersought.com/article/8311115057/).