cid#1546393 SBSC: String concatenation in loop using + operator

Change-Id: I697830e97b3168aab3e41e96b744ab80edbad31c
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/157401
Tested-by: Jenkins
Reviewed-by: Caolán McNamara <caolan.mcnamara@collabora.com>

ridljar/com/sun/star/lib/connections/websocket/WebsocketConnection.java

@@ -279,7 +279,7 @@ public class WebsocketConnection extends WebSocketClient implements XConnection,
     public void onMessage(ByteBuffer message) {
         byte[] prefixedMessageBytes = message.array();
 
-        String messageType = "";
+        StringBuffer messageTypeBuf = new StringBuffer();
         boolean hasType = false;
         int i;
         for (i = 0; i < prefixedMessageBytes.length - 1; i++) {
@@ -287,7 +287,7 @@ public class WebsocketConnection extends WebSocketClient implements XConnection,
                 hasType = true;
                 break;  // The type ends with ": ", so if we find this sequence we found the end of our type
             }
-            messageType += (char)prefixedMessageBytes[i];
+            messageTypeBuf.append((char)prefixedMessageBytes[i]);
         }
 
         if(!hasType) {
@@ -295,6 +295,8 @@ public class WebsocketConnection extends WebSocketClient implements XConnection,
             return;
         }
 
+        String messageType = messageTypeBuf.toString();
+
         int messageStartIndex = i + 2;
 
         if (!messageType.equals("urp")) {