You can watch all new source code published at @RafaDelNero with #JavaChallenge.
Check the solutions from the Java Challengers code at Java Challengers Videos
Using the common way:
docker run --rm -v $(pwd):/app -w /app/src/main/java openjdk:13-slim java --enable-preview --source 13 function/FunctionalInterfaceChallenge.java
Using the Docker Compose:
docker-compose run --rm java-source crazysyntax/NameChallenge.java