More idiomatic code in Stream API

Change-Id: Ifa5a311cfc1ce43f5eab80be9ddce5fa36e47d92

@@ -40,6 +40,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
+import java.util.function.Function;
 import java.util.stream.Collectors;
 
 class MockResourceService implements ResourceService {
@@ -49,7 +50,7 @@ class MockResourceService implements ResourceService {
     @Override
     public List<ResourceAllocation> allocate(ResourceConsumer consumer, List<Resource> resources) {
         assignment.putAll(
-                resources.stream().collect(Collectors.toMap(x -> x, x -> consumer))
+                resources.stream().collect(Collectors.toMap(Function.identity(), x -> consumer))
         );
 
         return resources.stream()

@@ -50,6 +50,7 @@ import org.slf4j.Logger;
 
 import java.util.Collection;
 import java.util.Map;
+import java.util.function.Function;
 import java.util.stream.Collectors;
 
 import static org.slf4j.LoggerFactory.getLogger;
@@ -209,7 +210,7 @@ public class MeterManager extends AbstractListenerProviderRegistry<MeterEvent, M
             //FIXME: FOLLOWING CODE CANNOT BE TESTED UNTIL SOMETHING THAT
             //FIXME: IMPLEMENTS METERS EXISTS
             Map<Pair<DeviceId, MeterId>, Meter> storedMeterMap = store.getAllMeters().stream()
-                    .collect(Collectors.toMap(m -> Pair.of(m.deviceId(), m.id()), m -> m));
+                    .collect(Collectors.toMap(m -> Pair.of(m.deviceId(), m.id()), Function.identity()));
 
             meterEntries.stream()
                     .filter(m -> storedMeterMap.remove(Pair.of(m.deviceId(), m.id())) != null)