I fixed some NPE in version 0.3.
But I found that parsing code is not enough to detect bugs. For example, we cannot know the difference between:
// this is OK, both of placeholder and parameter is only one logger.info("UserId is: {}", new UserId()); // this is a bug, because there is no parameter for placeholder logger.info("UserId is: {}", new OriginalException());
I think we should parse .class file instead of source. So using FindBugs is better than using PMD.