Sonar fixes

Rule: Use isEmpty() to check whether the collection is empty or not.

Change-Id: Ib5ab56b2263623b297db56c5cac2c2ee80e12725
diff --git a/apps/mfwd/src/main/java/org/onosproject/mfwd/impl/McastForwarding.java b/apps/mfwd/src/main/java/org/onosproject/mfwd/impl/McastForwarding.java
index c7326b8..16d7da3 100644
--- a/apps/mfwd/src/main/java/org/onosproject/mfwd/impl/McastForwarding.java
+++ b/apps/mfwd/src/main/java/org/onosproject/mfwd/impl/McastForwarding.java
@@ -235,7 +235,7 @@
 
             ArrayList<ConnectPoint> egressList = (ArrayList<ConnectPoint>) mcastRouteManager.fetchSinks(mRoute);
             //If there are no egress ports set return, otherwise forward the packets to their expected port.
-            if (egressList.size() == 0) {
+            if (egressList.isEmpty()) {
                 return;
             }
 
diff --git a/apps/pce/pceweb/src/main/java/org/onosproject/pceweb/PceWebTopovMessageHandler.java b/apps/pce/pceweb/src/main/java/org/onosproject/pceweb/PceWebTopovMessageHandler.java
index 8e93b80..c1a1bec 100644
--- a/apps/pce/pceweb/src/main/java/org/onosproject/pceweb/PceWebTopovMessageHandler.java
+++ b/apps/pce/pceweb/src/main/java/org/onosproject/pceweb/PceWebTopovMessageHandler.java
@@ -710,7 +710,7 @@
         Highlights highlights = new Highlights();
         paths.removeAll(paths);
         tunnelSet = tunnelService.queryTunnel(MPLS);
-        if (tunnelSet.size() == 0) {
+        if (tunnelSet.isEmpty()) {
             log.warn("Tunnel does not exist");
             sendMessage(highlightsMessage(highlights));
             return;
diff --git a/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/RoutingRulePopulator.java b/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/RoutingRulePopulator.java
index 9e215a9..b691f80 100644
--- a/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/RoutingRulePopulator.java
+++ b/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/RoutingRulePopulator.java
@@ -559,7 +559,7 @@
         }
 
         List<Port> devPorts = srManager.deviceService.getPorts(deviceId);
-        if (devPorts == null || devPorts.size() == 0) {
+        if (devPorts == null || devPorts.isEmpty()) {
             log.warn("Device {} ports not available. Unable to add MacVlan filters",
                      deviceId);
             return null;
diff --git a/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/config/DeviceConfiguration.java b/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/config/DeviceConfiguration.java
index 7eb6894..2bd9932 100644
--- a/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/config/DeviceConfiguration.java
+++ b/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/config/DeviceConfiguration.java
@@ -357,7 +357,7 @@
                         .map(IpPrefix::getIp4Prefix)
                         .collect(Collectors.toSet());
 
-        if (subnets.size() == 0) {
+        if (subnets.isEmpty()) {
             log.info(NO_SUBNET, connectPoint);
             return null;
         } else if (subnets.size() > 1) {
diff --git a/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/grouphandler/DefaultGroupHandler.java b/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/grouphandler/DefaultGroupHandler.java
index 52606cf..b76a04c 100644
--- a/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/grouphandler/DefaultGroupHandler.java
+++ b/apps/segmentrouting/src/main/java/org/onosproject/segmentrouting/grouphandler/DefaultGroupHandler.java
@@ -655,7 +655,7 @@
                     log.warn("Neighbor {} is not in the port map yet for dev:{}",
                              neighborId, deviceId);
                     return;
-                } else if (devicePortMap.get(neighborId).size() == 0) {
+                } else if (devicePortMap.get(neighborId).isEmpty()) {
                     log.warn("There are no ports for "
                             + "the Device {} in the port map yet", neighborId);
                     return;
diff --git a/apps/test/intent-perf/src/main/java/org/onosproject/intentperf/IntentPerfInstaller.java b/apps/test/intent-perf/src/main/java/org/onosproject/intentperf/IntentPerfInstaller.java
index 9b758d4..b4d7acf 100644
--- a/apps/test/intent-perf/src/main/java/org/onosproject/intentperf/IntentPerfInstaller.java
+++ b/apps/test/intent-perf/src/main/java/org/onosproject/intentperf/IntentPerfInstaller.java
@@ -358,7 +358,7 @@
                 .forEach(device -> devices.put(mastershipService.getMasterFor(device.id()), device));
 
         // ensure that we have at least one device per neighbor
-        neighbors.forEach(node -> checkState(devices.get(node).size() > 0,
+        neighbors.forEach(node -> checkState(!devices.get(node).isEmpty(),
                                              "There are no devices for {}", node));
 
         // TODO pull this outside so that createIntent can use it
diff --git a/apps/vtn/vtnmgr/src/main/java/org/onosproject/vtn/table/impl/L2ForwardServiceImpl.java b/apps/vtn/vtnmgr/src/main/java/org/onosproject/vtn/table/impl/L2ForwardServiceImpl.java
index 7c9c30d..582aad3 100644
--- a/apps/vtn/vtnmgr/src/main/java/org/onosproject/vtn/table/impl/L2ForwardServiceImpl.java
+++ b/apps/vtn/vtnmgr/src/main/java/org/onosproject/vtn/table/impl/L2ForwardServiceImpl.java
@@ -142,7 +142,7 @@
                     .withSelector(selector).fromApp(appId).makePermanent()
                     .withFlag(Flag.SPECIFIC).withPriority(MAC_PRIORITY);
             if (type.equals(Objective.Operation.ADD)) {
-                if (Sets.newHashSet(localVmPorts).size() == 0) {
+                if (Sets.newHashSet(localVmPorts).isEmpty()) {
                     flowObjectiveService.forward(deviceId, objective.remove());
                 } else {
                     flowObjectiveService.forward(deviceId, objective.add());
diff --git a/apps/vtn/vtnmgr/src/main/java/org/onosproject/vtn/util/VtnData.java b/apps/vtn/vtnmgr/src/main/java/org/onosproject/vtn/util/VtnData.java
index 2ee889a..c66cba6 100644
--- a/apps/vtn/vtnmgr/src/main/java/org/onosproject/vtn/util/VtnData.java
+++ b/apps/vtn/vtnmgr/src/main/java/org/onosproject/vtn/util/VtnData.java
@@ -137,7 +137,7 @@
                     }
                 }
             });
-            if (vPorts.size() == 0) {
+            if (vPorts.isEmpty()) {
                 return null;
             }
             return vPorts.get(0);
@@ -168,7 +168,7 @@
                             }
                         }
                     });
-            if (vPorts.size() == 0) {
+            if (vPorts.isEmpty()) {
                 return null;
             }
             return vPorts.get(0);
diff --git a/apps/vtn/vtnrsc/src/main/java/org/onosproject/vtnrsc/virtualport/impl/VirtualPortManager.java b/apps/vtn/vtnrsc/src/main/java/org/onosproject/vtnrsc/virtualport/impl/VirtualPortManager.java
index ede595f..0b7d0a6 100644
--- a/apps/vtn/vtnrsc/src/main/java/org/onosproject/vtnrsc/virtualport/impl/VirtualPortManager.java
+++ b/apps/vtn/vtnrsc/src/main/java/org/onosproject/vtnrsc/virtualport/impl/VirtualPortManager.java
@@ -181,7 +181,7 @@
                 }
             }
         });
-        if (vPorts.size() == 0) {
+        if (vPorts.isEmpty()) {
             return null;
         }
         return vPorts.get(0);
@@ -196,7 +196,7 @@
                 vPorts.add(p);
             }
         });
-        if (vPorts.size() == 0) {
+        if (vPorts.isEmpty()) {
             return null;
         }
         return vPorts.get(0);
@@ -217,7 +217,7 @@
                         }
                     }
                 });
-        if (vPorts.size() == 0) {
+        if (vPorts.isEmpty()) {
             return null;
         }
         return vPorts.get(0);
diff --git a/apps/vtn/vtnweb/src/main/java/org/onosproject/vtnweb/resources/FloatingIpWebResource.java b/apps/vtn/vtnweb/src/main/java/org/onosproject/vtnweb/resources/FloatingIpWebResource.java
index c2c4632..8691b42 100644
--- a/apps/vtn/vtnweb/src/main/java/org/onosproject/vtnweb/resources/FloatingIpWebResource.java
+++ b/apps/vtn/vtnweb/src/main/java/org/onosproject/vtnweb/resources/FloatingIpWebResource.java
@@ -99,7 +99,7 @@
                 .getFloatingIp(FloatingIpId.of(id)), GET_FAIL);
 
         ObjectNode result = new ObjectMapper().createObjectNode();
-        if (fields.size() > 0) {
+        if (!fields.isEmpty()) {
             result.set("floatingip",
                        new FloatingIpCodec().extracFields(sub, this, fields));
         } else {
diff --git a/apps/vtn/vtnweb/src/main/java/org/onosproject/vtnweb/resources/RouterWebResource.java b/apps/vtn/vtnweb/src/main/java/org/onosproject/vtnweb/resources/RouterWebResource.java
index 855209c..332bd41 100644
--- a/apps/vtn/vtnweb/src/main/java/org/onosproject/vtnweb/resources/RouterWebResource.java
+++ b/apps/vtn/vtnweb/src/main/java/org/onosproject/vtnweb/resources/RouterWebResource.java
@@ -106,7 +106,7 @@
                 .getRouter(RouterId.valueOf(id)), NOT_EXIST);
 
         ObjectNode result = new ObjectMapper().createObjectNode();
-        if (fields.size() > 0) {
+        if (!fields.isEmpty()) {
             result.set("router",
                        new RouterCodec().extracFields(sub, this, fields));
         } else {