Comment out line 18 to go with TLS. Add --add-opens=java.base/java.nio=ALL-UNNAMED to MAVEN_OPTS, then run with mvn compile exec:java.
To connect through TLS, set the USE_TLS system variable to any value (for example export USE_TLS=1).
This code is supposed to work with the Arrow RS Flight SQL example
Expected output (besides tons of log messages) is Hello, FlightSQL!