Use dianmond operator

Change-Id: I551dd9443b10ef17832f74a554486b7605e9866a
diff --git a/apps/vtnweb/src/main/java/org/onosproject/vtnweb/resources/TenantNetworkWebResource.java b/apps/vtnweb/src/main/java/org/onosproject/vtnweb/resources/TenantNetworkWebResource.java
index 9fd75ab..cd2ac29 100644
--- a/apps/vtnweb/src/main/java/org/onosproject/vtnweb/resources/TenantNetworkWebResource.java
+++ b/apps/vtnweb/src/main/java/org/onosproject/vtnweb/resources/TenantNetworkWebResource.java
@@ -240,7 +240,7 @@
     @Path("{id}")

     public Response deleteNetworks(@PathParam("id") String id) {

         log.debug("Deletes network by identifier {}.", id);

-        Set<TenantNetworkId> networkSet = new HashSet<TenantNetworkId>();

+        Set<TenantNetworkId> networkSet = new HashSet<>();

         networkSet.add(TenantNetworkId.networkId(id));

         Boolean issuccess = nullIsNotFound(get(TenantNetworkService.class)

                 .removeNetworks(networkSet), NETWORK_NOT_FOUND);