Return singleton empty collection instead of null in Read service code

[controller.git] / opendaylight / protocol_plugins / openflow / src / main / java / org / opendaylight / controller / protocol_plugin / openflow / internal / ReadService.java

diff --git a/opendaylight/protocol_plugins/openflow/src/main/java/org/opendaylight/controller/protocol_plugin/openflow/internal/ReadService.java b/opendaylight/protocol_plugins/openflow/src/main/java/org/opendaylight/controller/protocol_plugin/openflow/internal/ReadService.java
index 215216e25f00a8fb3f9538d59902d9daa5e86357..f1f5944f379cdd96bf49e2293a52cb1e1d111277 100644 (file)
--- a/opendaylight/protocol_plugins/openflow/src/main/java/org/opendaylight/controller/protocol_plugin/openflow/internal/ReadService.java
+++ b/opendaylight/protocol_plugins/openflow/src/main/java/org/opendaylight/controller/protocol_plugin/openflow/internal/ReadService.java
@@ -9,6 +9,7 @@
 
 package org.opendaylight.controller.protocol_plugin.openflow.internal;
 
+import java.util.Collections;
 import java.util.Dictionary;
 import java.util.List;
 import java.util.Set;
@@ -122,12 +123,12 @@ public class ReadService implements IPluginInReadService, IReadFilterInternalLis
     public List<FlowOnNode> readAllFlow(Node node, boolean cached) {
         if (!node.getType().equals(NodeIDType.OPENFLOW)) {
             logger.error("Invalid node type");
-            return null;
+            return Collections.emptyList();
         }
 
         if (!connectionOutService.isLocal(node)) {
             logger.debug("This Controller is not the master for the node : " + node);
-            return null;
+            return Collections.emptyList();
         }
 
         return filter.readAllFlow(containerName, node, cached);
@@ -170,12 +171,12 @@ public class ReadService implements IPluginInReadService, IReadFilterInternalLis
             boolean cached) {
         if (!node.getType().equals(NodeIDType.OPENFLOW)) {
             logger.error("Invalid node type");
-            return null;
+            return Collections.emptyList();
         }
 
         if (!connectionOutService.isLocal(node)) {
             logger.debug("This Controller is not the master for node : " + node);
-            return null;
+            return Collections.emptyList();
         }
 
         return filter.readAllNodeConnector(containerName, node, cached);
@@ -217,12 +218,12 @@ public class ReadService implements IPluginInReadService, IReadFilterInternalLis
     public List<NodeTableStatistics> readAllNodeTable(Node node, boolean cached) {
         if (!node.getType().equals(NodeIDType.OPENFLOW)) {
             logger.error("Invalid node type");
-            return null;
+            return Collections.emptyList();
         }
 
         if (!connectionOutService.isLocal(node)) {
             logger.debug("This Controller is not the master for node : " + node);
-            return null;
+            return Collections.emptyList();
         }
 
         return filter.readAllNodeTable(containerName, node, cached);