When compiling code that depends on Guava 21.0, [Edit: I mistakenly said 20.0 originally] using Maven, I get many warning messages like this:

Cannot find annotation method 'value()' in type 'com.google.errorprone.annotations.CompatibleWith': class file for com.google.errorprone.annotations.CompatibleWith not found

I do not use the errorprone library in my code, so this error message is due to its use by Guava.

Obviously, these are only warning messages and are not critical.