And with templates, you do log.debug("{} {}", var1, var2, someThrowable) and don't even call toString on those unless you're actually logging them. Compare thi

And with templates, you do log.debug("{} {}", var1, var2, someThrowable) and don't even call toString on those unless you're actually logging them. Compare this to system.err.println("DEBUG: " + var1 + " " + var2 + " " + someThrowable.stackTrace()) -- that creates a StringBuilder, allocates a potentially large String, and then sends it on. There are numerous performance impacts (improvements) at using a logging framework that doesn't log or allocate a String to log what it doesn't need to.