Use chained String.append calls.

src/main/java/org/torproject/metrics/exonerator/ExoneraTorDatabaseImporter.java

@@ -145,7 +145,7 @@ public class ExoneraTorDatabaseImporter {
       }
       BufferedWriter bw = new BufferedWriter(new FileWriter(
           "exonerator-lock"));
-      bw.append(String.valueOf(System.currentTimeMillis()) + "\n");
+      bw.append(String.valueOf(System.currentTimeMillis())).append("\n");
       bw.close();
     } catch (IOException e) {
       logger.warn("Could not create 'exonerator-lock' file.  Exiting.");

src/main/java/org/torproject/metrics/exonerator/ExoneraTorServlet.java

@@ -110,7 +110,7 @@ public class ExoneraTorServlet extends HttpServlet {
               StringBuilder sb = new StringBuilder();
               int writtenAddresses = 0;
               for (String address : match.addresses) {
-                sb.append((writtenAddresses++ > 0 ? ", " : "") + address);
+                sb.append(writtenAddresses++ > 0 ? ", " : "").append(address);
               }
               String[] statusEntry = new String[]{match.timestamp,
                   sb.toString(), match.fingerprint, match.nickname,