Java Util Logging does not support varargs so we have to write some ugly
LOGGER.log(Level.INFO, "{0} : {1}", new Object[] { "first", "last" })

There's tons of logging framework but slf4j is a widely adopted one, and allows to just write
LOGGER.info("{0} : {1}", first, last)

Also, the log output to use 2 lines per log message (one for timestamp, next for message content) is a pain when you want to filter the log. Moving to a single line format would help jenkins support efficiency