diff --git a/src/main/java/net/onrc/onos/core/datastore/DataStoreClient.java b/src/main/java/net/onrc/onos/core/datastore/DataStoreClient.java
index be9fce5..b5c1ae7 100644
--- a/src/main/java/net/onrc/onos/core/datastore/DataStoreClient.java
+++ b/src/main/java/net/onrc/onos/core/datastore/DataStoreClient.java
@@ -4,7 +4,7 @@
 import net.onrc.onos.core.datastore.ramcloud.RCClient;
 
 // This class probably need to be a service
-public class DataStoreClient {
+public final class DataStoreClient {
     private static final String BACKEND = System.getProperty("net.onrc.onos.core.datastore.backend", "hazelcast");
 
     // Suppresses default constructor, ensuring non-instantiability.
diff --git a/src/main/java/net/onrc/onos/core/datastore/hazelcast/HZClient.java b/src/main/java/net/onrc/onos/core/datastore/hazelcast/HZClient.java
index 4cc68b4..32ff15b 100644
--- a/src/main/java/net/onrc/onos/core/datastore/hazelcast/HZClient.java
+++ b/src/main/java/net/onrc/onos/core/datastore/hazelcast/HZClient.java
@@ -30,7 +30,7 @@
 import com.hazelcast.core.HazelcastInstance;
 import com.hazelcast.core.IMap;
 
-public class HZClient implements IKVClient {
+public final class HZClient implements IKVClient {
     private static final Logger log = LoggerFactory.getLogger(HZClient.class);
 
     static final long VERSION_NONEXISTENT = 0L;
diff --git a/src/main/java/net/onrc/onos/core/datastore/utils/ByteArrayUtil.java b/src/main/java/net/onrc/onos/core/datastore/utils/ByteArrayUtil.java
index 32abb59..96d0048 100644
--- a/src/main/java/net/onrc/onos/core/datastore/utils/ByteArrayUtil.java
+++ b/src/main/java/net/onrc/onos/core/datastore/utils/ByteArrayUtil.java
@@ -2,7 +2,7 @@
 
 import java.nio.ByteBuffer;
 
-public class ByteArrayUtil {
+public final class ByteArrayUtil {
 
     // Suppresses default constructor, ensuring non-instantiability.
     private ByteArrayUtil() {
diff --git a/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java b/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java
index b9b093f..3f5326e 100644
--- a/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java
+++ b/src/main/java/net/onrc/onos/core/flowprogrammer/FlowPusher.java
@@ -82,7 +82,7 @@
  *
  * @author Naoki Shiota
  */
-public class FlowPusher implements IFlowPusherService, IOFMessageListener {
+public final class FlowPusher implements IFlowPusherService, IOFMessageListener {
     private static final Logger log = LoggerFactory.getLogger(FlowPusher.class);
     protected static final int DEFAULT_NUMBER_THREAD = 1;
 
@@ -239,7 +239,7 @@
      *
      * @author Naoki
      */
-    private static class BarrierInfo {
+    private static final class BarrierInfo {
         final long dpid;
         final int xid;