Startup of geoserver-2.13.0-bin.zip with Java 9 contains a handled NumberFormatException. Curiously, his does not affect Java 8 or Java 10.
The failure to start with ClassNotFoundException for JAXBException reported separately as GEOS-8748.
$ java -version
openjdk version "9.0.4"
OpenJDK Runtime Environment (build 9.0.4+12-Debian-4)
OpenJDK 64-Bit Server VM (build 9.0.4+12-Debian-4, mixed mode)