Fix some pmd high priority errors

Change-Id: Ieb38cdbe1dd2c47515976850b7e5edf8c35674da
diff --git a/src/main/java/net/onrc/onos/core/intent/FlowEntry.java b/src/main/java/net/onrc/onos/core/intent/FlowEntry.java
index 0fd618e..2307e65 100644
--- a/src/main/java/net/onrc/onos/core/intent/FlowEntry.java
+++ b/src/main/java/net/onrc/onos/core/intent/FlowEntry.java
@@ -244,7 +244,7 @@
      * Generates hash using Objects.hash() on the match and actions.
      */
     @Override
-    public int hashCode() {
+    public final int hashCode() {
         return Objects.hash(match, actions);
     }