Moved redundant texts to constants

components/device-mgt/org.wso2.carbon.device.mgt.api/src/main/java/org/wso2/carbon/device/mgt/jaxrs/api/impl/GroupImpl.java

@@ -50,6 +50,9 @@ import java.util.List;
 @SuppressWarnings("NonJaxWsWebServices")
 public class GroupImpl implements Group {
 
+    private static final String GROUP_CANNOT_NULL_MSG = "Group cannot be null.";
+    private static final String GROUP_NAME_INVALID_MSG = "Provided group name is invalid. Should be in minimum 3 " +
+                                                         "characters long and should not include any whitespaces.";
     private static Log log = LogFactory.getLog(GroupImpl.class);
 
     @Override
@@ -58,11 +61,9 @@ public class GroupImpl implements Group {
     public Response createGroup(DeviceGroup group) {
         String owner = PrivilegedCarbonContext.getThreadLocalCarbonContext().getUsername();
         if (group == null) {
-            return Response.status(Response.Status.BAD_REQUEST).entity("Group cannot be null").build();
+            return Response.status(Response.Status.BAD_REQUEST).entity(GROUP_CANNOT_NULL_MSG).build();
         } else if (group.getName() == null || !group.getName().matches("^[\\S]{3,30}$")) {
-            String msg = "Provided group name is invalid. Should be in minimum 3 characters long " +
-                         "and should not include any whitespaces.";
-            return Response.status(Response.Status.BAD_REQUEST).entity(msg).build();
+            return Response.status(Response.Status.BAD_REQUEST).entity(GROUP_NAME_INVALID_MSG).build();
         }
         group.setOwner(owner);
         group.setDateOfCreation(new Date().getTime());
@@ -98,9 +99,7 @@ public class GroupImpl implements Group {
     public Response updateGroup(@PathParam("groupName") String groupName, @PathParam("owner") String owner,
                                 DeviceGroup group) {
         if (group.getName() == null || !group.getName().matches("^[\\S]{3,30}$")) {
-            String msg = "Provided group name is invalid. Should be in minimum 3 characters long " +
-                         "and should not include any whitespaces.";
-            return Response.status(Response.Status.BAD_REQUEST).entity(msg).build();
+            return Response.status(Response.Status.BAD_REQUEST).entity(GROUP_NAME_INVALID_MSG).build();
         }
         try {
             DeviceMgtAPIUtils.getGroupManagementProviderService().updateGroup(group, groupName, owner);