I find the behavior of logger.whatever(format, ....) rather confusing.

1. What bothers me most: Forgetting a brace means that an argument gets ignored, which may mean waiting one more week till something like

logger.error("Rare problem: {}, problem, details)

fires again. A simple fix would be to follow Guava's implementation like in

https://github.com/google/guava/blob/master/guava/src/com/google/common/base/Preconditions.java#L154

which says "Unmatched arguments will be appended to the formatted message in square braces".

This is a simple fix and the behavior gets changed only in case of a user error. I'd gladly contribute the fix.

2. A strange thing is that an exception needs no braces. So

logger.info("Foo {} bar {}", o1, o2)

leaves {} behind if o2 happens to be an exception. This is no big deal, but it's undocumented. My logfiles are full of braces as it took me a while till I found it out.