Defer logging message build to Logger

Instead of writing:

LOG.debug("my debug message is " + var1 + " " + var2 + ": " + var3 ); 

one should write:

LOG.debug("my debug message is {} {}: {}", var1, var2, var3); 

And only if the level is really activated, then the message String should actually be build.

see also two discussions:
http://n2.nabble.com/Logging-architecture-proposal-tt516791.html#none
http://n2.nabble.com/Hibernate-3.3.1-upgrade--tt1084964.html

It could also be argued, since at the moment String.format is used, that this form of String (eg '%s') could be used instead of '{}' .