Make field final

Change-Id: I19f2ad98e56352570478a66f896c1e9c6a3573e5
diff --git a/core/net/src/main/java/org/onosproject/net/flow/impl/FlowRuleManager.java b/core/net/src/main/java/org/onosproject/net/flow/impl/FlowRuleManager.java
index 880b4fc..ccbbd4a 100644
--- a/core/net/src/main/java/org/onosproject/net/flow/impl/FlowRuleManager.java
+++ b/core/net/src/main/java/org/onosproject/net/flow/impl/FlowRuleManager.java
@@ -129,8 +129,7 @@
 
     private IdGenerator idGenerator;
 
-    private Map<Long, FlowOperationsProcessor> pendingFlowOperations
-            = new ConcurrentHashMap<>();
+    private final Map<Long, FlowOperationsProcessor> pendingFlowOperations = new ConcurrentHashMap<>();
 
     @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
     protected FlowRuleStore store;