KNOX-1997 - Fix diamond operator compiliation error

Signed-off-by: Kevin Risden <krisden@apache.org>
diff --git a/gateway-server/src/main/java/org/apache/knox/gateway/websockets/ProxyWebSocketAdapter.java b/gateway-server/src/main/java/org/apache/knox/gateway/websockets/ProxyWebSocketAdapter.java
index 6364a01..4274e6e 100644
--- a/gateway-server/src/main/java/org/apache/knox/gateway/websockets/ProxyWebSocketAdapter.java
+++ b/gateway-server/src/main/java/org/apache/knox/gateway/websockets/ProxyWebSocketAdapter.java
@@ -64,7 +64,7 @@
 
   /* Message buffer for holding data frames temporarily in memory till connection is setup.
    Keeping the max size of the buffer as 100 messages for now. */
-  private List<String> messageBuffer = new ArrayList<String>();
+  private List<String> messageBuffer = new ArrayList<>();
   private Lock remoteLock = new ReentrantLock();
 
   private final GatewayConfig config;