Update checkstyle to version 6.19

Change-Id: I32787f2a5f4f4b17fd4cdcf9bd2eb3903dcecfff
diff --git a/core/store/primitives/src/test/java/org/onosproject/store/primitives/resources/impl/AtomixConsistentTreeMapTest.java b/core/store/primitives/src/test/java/org/onosproject/store/primitives/resources/impl/AtomixConsistentTreeMapTest.java
index a3e75a3..f27148e 100644
--- a/core/store/primitives/src/test/java/org/onosproject/store/primitives/resources/impl/AtomixConsistentTreeMapTest.java
+++ b/core/store/primitives/src/test/java/org/onosproject/store/primitives/resources/impl/AtomixConsistentTreeMapTest.java
@@ -117,7 +117,7 @@
                                 result.value())).join());
         //test all compute methods in this section
         allKeys.forEach(key -> map.computeIfAbsent(
-                key, v ->allValues.get(allKeys.indexOf(key)
+                key, v -> allValues.get(allKeys.indexOf(key)
                 )).thenAccept(result ->
                                 assertArrayEquals(
                                         allValues.get(allKeys.indexOf(key)),
@@ -657,4 +657,4 @@
             return 0;
         }
     }
-}
\ No newline at end of file
+}