The classes in this directory contain errors.
We want to process as many of the files as possible and not
stop at the first error.
See the message thread at

https://groups.google.com/forum/#!topic/checker-framework-discuss/4A0Z3z8vcXA

Performing

javac -processor org.checkerframework.checker.nonnull.NonNullFbcChecker *.java

should result in 2 errors and 1 warning, not only 1 each.