Clean up source code of REST API

- Add missing @Produces annotation
- Correct comments
- Restrict variable access level

Change-Id: I7f75650b83651248370e7781b1e8aec7eac2314c
diff --git a/web/api/src/main/java/org/onosproject/rest/resources/MetersWebResource.java b/web/api/src/main/java/org/onosproject/rest/resources/MetersWebResource.java
index 34a014f..ffb9149 100644
--- a/web/api/src/main/java/org/onosproject/rest/resources/MetersWebResource.java
+++ b/web/api/src/main/java/org/onosproject/rest/resources/MetersWebResource.java
@@ -52,20 +52,20 @@
 public class MetersWebResource extends AbstractWebResource {
 
     @Context
-    UriInfo uriInfo;
+    private UriInfo uriInfo;
 
     private final Logger log = getLogger(getClass());
-    public static final String DEVICE_INVALID = "Invalid deviceId in meter creation request";
-    public static final String METER_NOT_FOUND = "Meter is not found for ";
+    private static final String DEVICE_INVALID = "Invalid deviceId in meter creation request";
+    private static final String METER_NOT_FOUND = "Meter is not found for ";
 
-    final MeterService meterService = get(MeterService.class);
-    final ObjectNode root = mapper().createObjectNode();
-    final ArrayNode metersNode = root.putArray("meters");
+    private final MeterService meterService = get(MeterService.class);
+    private final ObjectNode root = mapper().createObjectNode();
+    private final ArrayNode metersNode = root.putArray("meters");
 
     /**
      * Returns all meters of all devices.
      *
-     * @return array of all the meters in the system
+     * @return 200 OK with array of all the meters in the system
      * @onos.rsModel Meters
      */
     @GET
@@ -82,7 +82,7 @@
      * Returns a collection of meters by the device id.
      *
      * @param deviceId device identifier
-     * @return array of meters which belongs to specified device
+     * @return 200 OK with array of meters which belongs to specified device
      * @onos.rsModel Meters
      */
     @GET
@@ -102,7 +102,7 @@
      *
      * @param deviceId device identifier
      * @param meterId meter identifier
-     * @return a meter, return 404 if no entry has been found
+     * @return 200 OK with a meter, return 404 if no entry has been found
      * @onos.rsModel Meter
      */
     @GET
@@ -121,7 +121,7 @@
     }
 
     /**
-     * Create new meter rule. Creates and installs a new meter rule for the
+     * Creates new meter rule. Creates and installs a new meter rule for the
      * specified device.
      *
      * @param deviceId device identifier
@@ -182,7 +182,7 @@
     }
 
     /**
-     * Convert a meter instance to meterRequest instance with a certain operation.
+     * Converts a meter instance to meterRequest instance with a certain operation.
      *
      * @param meter     meter instance
      * @param operation operation