There is currently no way of overriding the Java executable used by {{clj}}/{{clojure}} on a per-invocation basis.
The {{clojure}} script uses the command {{type -p java}} to locate the {{java}} executable. Overriding is therefore possible by placing a symlink early on the shell's search {{PATH}}, but this isn't very convenient.
It would be useful to allow overriding using an environment variable, thus enabling invocations like {{JAVA_CMD=/path/to/java clj ...}}.