diff --git a/apps/cpman/app/src/main/java/org/onosproject/cpman/rest/SystemMetricsCollectorWebResource.java b/apps/cpman/app/src/main/java/org/onosproject/cpman/rest/SystemMetricsCollectorWebResource.java
index c96d1d9..5dd9413 100644
--- a/apps/cpman/app/src/main/java/org/onosproject/cpman/rest/SystemMetricsCollectorWebResource.java
+++ b/apps/cpman/app/src/main/java/org/onosproject/cpman/rest/SystemMetricsCollectorWebResource.java
@@ -106,31 +106,31 @@
             long cpuIdleTime = nullIsIllegal(jsonTree.get("cpuIdleTime").asLong(), INVALID_REQUEST);
 
             aggregator.setMetricsService(metricsService);
-            aggregator.addMetrics(Optional.ofNullable(null), SYSTEM_TYPE);
+            aggregator.addMetrics(Optional.empty(), SYSTEM_TYPE);
 
             cm = new ControlMetric(ControlMetricType.CPU_LOAD,
                     new MetricValue.Builder().load(cpuLoad).add());
-            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.ofNullable(null));
+            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.empty());
             aggregator.increment(ControlMetricType.CPU_LOAD, cpuLoad);
 
             cm = new ControlMetric(ControlMetricType.TOTAL_CPU_TIME,
                     new MetricValue.Builder().load(totalCpuTime).add());
-            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.ofNullable(null));
+            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.empty());
             aggregator.increment(ControlMetricType.TOTAL_CPU_TIME, totalCpuTime);
 
             cm = new ControlMetric(ControlMetricType.SYS_CPU_TIME,
                     new MetricValue.Builder().load(sysCpuTime).add());
-            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.ofNullable(null));
+            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.empty());
             aggregator.increment(ControlMetricType.SYS_CPU_TIME, sysCpuTime);
 
             cm = new ControlMetric(ControlMetricType.USER_CPU_TIME,
                     new MetricValue.Builder().load(userCpuTime).add());
-            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.ofNullable(null));
+            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.empty());
             aggregator.increment(ControlMetricType.USER_CPU_TIME, userCpuTime);
 
             cm = new ControlMetric(ControlMetricType.CPU_IDLE_TIME,
                     new MetricValue.Builder().load(cpuIdleTime).add());
-            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.ofNullable(null));
+            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.empty());
             aggregator.increment(ControlMetricType.CPU_IDLE_TIME, cpuIdleTime);
 
         } catch (IOException e) {
@@ -167,26 +167,26 @@
             long memFreeRatio = memTotal == 0L ? 0L : (memFree * PERCENT_CONSTANT) / memTotal;
 
             aggregator.setMetricsService(metricsService);
-            aggregator.addMetrics(Optional.ofNullable(null), SYSTEM_TYPE);
+            aggregator.addMetrics(Optional.empty(), SYSTEM_TYPE);
 
             cm = new ControlMetric(ControlMetricType.MEMORY_USED_RATIO,
                     new MetricValue.Builder().load(memUsedRatio).add());
-            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.ofNullable(null));
+            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.empty());
             aggregator.increment(ControlMetricType.MEMORY_USED_RATIO, memUsedRatio);
 
             cm = new ControlMetric(ControlMetricType.MEMORY_FREE_RATIO,
                     new MetricValue.Builder().load(memFreeRatio).add());
-            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.ofNullable(null));
+            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.empty());
             aggregator.increment(ControlMetricType.MEMORY_FREE_RATIO, memFreeRatio);
 
             cm = new ControlMetric(ControlMetricType.MEMORY_USED,
                     new MetricValue.Builder().load(memUsed).add());
-            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.ofNullable(null));
+            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.empty());
             aggregator.increment(ControlMetricType.MEMORY_USED, memUsed);
 
             cm = new ControlMetric(ControlMetricType.MEMORY_FREE,
                     new MetricValue.Builder().load(memFree).add());
-            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.ofNullable(null));
+            monitorService.updateMetric(cm, UPDATE_INTERVAL_IN_MINUTE, Optional.empty());
             aggregator.increment(ControlMetricType.MEMORY_FREE, memFree);
 
         } catch (IOException e) {