Minor Description
Threre are actively used @Nullable and @NotNull annotations in the project. They come to Drill from transitive dependencies javax.validation (validation-api-1.1.0.Final.jar) and javax.annotation (jsr305-3.0.1.jar), but Drill has not direct dependencies to them.
It is possible to add dependencies to this libraries, but possibly the better choice is to get rid from them and replace @NotNull annotation with Objects.requireNonNull() check in beginning of the method (the issue will be with methods in interfaces). Possibly the right decision to solve it could be raised in Drill dev mailing list.