The Java language specification (draft for version 8) §8.3 specifies a "UnannClassType" as
UnannClassType:
Identifier [TypeArguments]
UnannClassOrInterfaceType . {Annotation} Identifier [TypeArguments]
Thus, you need the declaration:
private transient org.apache.lucene.search.@Nullable Query cached_results;
Or in the augmented java 7 compiler of the checker framework:
private transient org.apache.lucene.search./*@Nullable*/ Query cached_results;
NOTE: normal Java compilers ignore /*@Nullable*/
.