Index: lucene/tools/forbiddenApis/base.txt
===================================================================
--- lucene/tools/forbiddenApis/base.txt	(revision 1550325)
+++ lucene/tools/forbiddenApis/base.txt	(working copy)
@@ -13,6 +13,8 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 
+java.lang.StringBuffer @ Use StringBuilder instead, which has no synchronization
+
 @defaultMessage Spawns threads with vague names; use a custom thread factory (Lucene's NamedThreadFactory, Solr's DefaultSolrThreadFactory) and name threads so that you can tell (by its name) which executor it is associated with
 java.util.concurrent.Executors#newFixedThreadPool(int)
 java.util.concurrent.Executors#newSingleThreadExecutor()