code: public static boolean fieldIsNonnull(Field field, AnnotationCache annotationCache) {
          Class<?> type = field.getDeclaringClass();
          if (annotationCache.hasFieldAnnotation(type, field.getName(), NONNULL)) {
              return true;
          }
          if (annotationCache.hasFieldAnnotation(type, field.getName(), NULLABLE)) {
              return false;
          }
          return annotationCache.hasClassAnnotation(type, FINDBUGS1X_DEFAULT_ANNOTATION_NONNULL) ||
                  annotationCache.hasClassAnnotation(type, JSR305_DEFAULT_ANNOTATION_NONNULL) ||
                  annotationCache.hasClassAnnotation(type, ECLIPSE_DEFAULT_ANNOTATION_NONNULL);
      }
docs: Checks whether the given field is marked with an Nonnull annotation,
  whether directly, or through some default annotation mechanism.
  
  @param field The field to be checked.
  @param annotationCache To provide access to the annotations on the field
  and the field's class
  @return True if the field is to be treated as Nonnull.