Unchecked cast from Object to Java 7

Question

I don't now Java can not understand where the mistake was. Using Java 7.

public void chatMessage(String userName, String message) {
      IScope scope = Red5.getConnectionLocal().getScope();
      ISharedObject chat = getSharedObject(scope, "chat");
      List<ChatHistoryItem> history = (List<ChatHistoryItem>) chat.getAttribute("remoteHistory");
      ChatHistoryItem item = new ChatHistoryItem();
      item.user = userName;
      item.date = new Date();
      item.message = message;
      history.add(item);
      chat.setAttribute("remoteHistory", history);
    }

error : Unchecked cast from Object to List<ChatHistoryItem>

Answer 1

The issue is because you cannot safely determine the type that will be returned by the ISharedObject.getAttribute method call. Which occurs in this line:

List<ChatHistoryItem> history = (List<ChatHistoryItem>) chat.getAttribute("remoteHistory");

If the object returned by this method is not of type List<ChatHistoryItem> you will receive a ClassCastException . If the method does return the appropriate type your code will still execute.

I am assuming this is not an error breaking your code, its just a warning from the IDE your using?