Consolidate throwing exception for disconnected websockets

Author: Petersoj

README.md

@@ -162,6 +162,7 @@ alpacaAPI.broker().trading()
                         .side(OrderSide.SELL)
                         .timeInForce(TimeInForce.GTC)
                         .type(OrderType.MARKET));
+
 // Wait to be filled
 Thread.sleep(2000);
 

src/main/java/net/jacobpeterson/alpaca/websocket/AlpacaWebsocket.java

@@ -209,6 +209,9 @@ protected void cleanupState() {
      * @param message the message
      */
     protected void sendWebsocketMessage(String message) {
+        if (!isConnected()) {
+            throw new IllegalStateException("This websocket must be connected before send a message!");
+        }
         LOGGER.trace("Websocket message sent: {}", message);
         websocket.send(message);
     }

src/main/java/net/jacobpeterson/alpaca/websocket/updates/UpdatesWebsocket.java

@@ -153,9 +153,6 @@ public void subscribeToTradeUpdates(boolean subscribe) {
     }
 
     private void sendTradeUpdatesListenMessage() {
-        if (!isConnected()) {
-            throw new IllegalStateException("This websocket must be connected before subscribing to streams!");
-        }
         final JsonObject requestObject = new JsonObject();
         requestObject.addProperty("action", "listen");
         final JsonArray streamsArray = new JsonArray();