Sonar fixes

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

Change-Id: Ib5ab56b2263623b297db56c5cac2c2ee80e12725
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